Fix error at shutdown when closing core sessions

11:30:06,617 INFO  [StandardService] Stopping service Catalina
11:30:06,659 ERROR [BundleRegistry] Failed to stop bundle org.nuxeo.runtime
org.osgi.framework.BundleException: Failed to stop activator: org.nuxeo.runtime.osgi.OSGiRuntimeActivator
	at org.nuxeo.osgi.BundleImpl.shutdown(BundleImpl.java:327)
	at org.nuxeo.osgi.BundleRegistry.shutdown(BundleRegistry.java:209)
	at org.nuxeo.osgi.OSGiAdapter.shutdown(OSGiAdapter.java:154)
	at org.nuxeo.osgi.application.loader.FrameworkLoader.doStop(FrameworkLoader.java:248)
	at org.nuxeo.osgi.application.loader.FrameworkLoader.stop(FrameworkLoader.java:136)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.nuxeo.osgi.application.FrameworkBootstrap.stop(FrameworkBootstrap.java:138)
	at org.nuxeo.runtime.tomcat.NuxeoLauncher.handleEvent(NuxeoLauncher.java:119)
	at org.nuxeo.runtime.tomcat.NuxeoLauncher.lifecycleEvent(NuxeoLauncher.java:92)
	at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:117)
	at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90)
	at org.apache.catalina.util.LifecycleBase.setStateInternal(LifecycleBase.java:394)
	at org.apache.catalina.util.LifecycleBase.setState(LifecycleBase.java:339)
	at org.apache.catalina.core.StandardContext.stopInternal(StandardContext.java:5751)
	at org.apache.catalina.util.LifecycleBase.stop(LifecycleBase.java:224)
	at org.apache.catalina.core.ContainerBase$StopChild.call(ContainerBase.java:1588)
	at org.apache.catalina.core.ContainerBase$StopChild.call(ContainerBase.java:1577)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.IllegalArgumentException: interface org.nuxeo.ecm.core.storage.sql.Mapper is not visible from class loader
	at java.lang.reflect.Proxy$ProxyClassFactory.apply(Proxy.java:581)
	at java.lang.reflect.Proxy$ProxyClassFactory.apply(Proxy.java:557)
	at java.lang.reflect.WeakCache$Factory.get(WeakCache.java:230)
	at java.lang.reflect.WeakCache.get(WeakCache.java:127)
	at java.lang.reflect.Proxy.getProxyClass0(Proxy.java:419)
	at java.lang.reflect.Proxy.newProxyInstance(Proxy.java:719)
	at org.nuxeo.ecm.core.storage.sql.jdbc.JDBCMapperConnector.newConnector(JDBCMapperConnector.java:94)
	at org.nuxeo.ecm.core.storage.sql.jdbc.JDBCBackend.newMapper(JDBCBackend.java:148)
	at org.nuxeo.ecm.core.storage.sql.RepositoryImpl.newMapper(RepositoryImpl.java:269)
	at org.nuxeo.ecm.core.storage.sql.VCSLockManager.getMapper(VCSLockManager.java:129)
	at org.nuxeo.ecm.core.storage.sql.VCSLockManager.closeLockManager(VCSLockManager.java:142)
	at org.nuxeo.ecm.core.storage.sql.RepositoryImpl.closeAllSessions(RepositoryImpl.java:425)
	at org.nuxeo.ecm.core.storage.sql.RepositoryImpl.close(RepositoryImpl.java:399)
	at org.nuxeo.ecm.core.storage.sql.ra.ManagedConnectionFactoryImpl.shutdown(ManagedConnectionFactoryImpl.java:257)
	at org.nuxeo.ecm.core.storage.sql.ra.ConnectionFactoryImpl.shutdown(ConnectionFactoryImpl.java:177)
	at org.nuxeo.ecm.core.repository.RepositoryService.shutdown(RepositoryService.java:59)
	at org.nuxeo.ecm.core.repository.RepositoryService$1.handleEvent(RepositoryService.java:80)
	at org.nuxeo.runtime.api.Framework.sendEvent(Framework.java:369)
	at org.nuxeo.runtime.AbstractRuntimeService.stop(AbstractRuntimeService.java:159)
	at org.nuxeo.runtime.api.Framework.shutdown(Framework.java:191)
	at org.nuxeo.runtime.osgi.OSGiRuntimeActivator.stop(OSGiRuntimeActivator.java:98)
	at org.nuxeo.osgi.BundleImpl.shutdown(BundleImpl.java:320)
	... 23 more