Fix infinite loop in Studio update from admin page

"http-bio-0.0.0.0-8080-exec-1" #98 daemon prio=5 os_prio=0 tid=0x00007fc6fc016000 nid=0x254a sleeping[0x00007fc67a6f7000]
   java.lang.Thread.State: TIMED_WAITING (sleeping)
        at java.lang.Thread.sleep(Native Method)
        at org.nuxeo.connect.client.jsf.AppCenterViewsManager$StudioAutoInstaller.run(AppCenterViewsManager.java:512)
        at org.nuxeo.connect.client.jsf.AppCenterViewsManager.installStudioSnapshot(AppCenterViewsManager.java:245)
        at org.nuxeo.connect.client.jsf.AppCenterViewsManager.installStudioSnapshotAndRedirect(AppCenterViewsManager.java:226)
        (...)
        at org.nuxeo.connect.client.jsf.AppCenterViewsManager_$$_javassist_seam_35.installStudioSnapshotAndRedirect(AppCenterViewsManager_$$_javassist_seam_35.java)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

= Component Loading Status: Pending: 0 / Unstarted: 0 / Total: 604
======================================================================
2016-01-18 13:01:07,780 INFO  [http-bio-0.0.0.0-8080-exec-1] [org.nuxeo.runtime.reload.ReloadComponent] Flush caches
2016-01-18 13:01:07,781 INFO  [http-bio-0.0.0.0-8080-exec-1] [org.nuxeo.runtime.reload.ReloadComponent] about to passivate for flush
2016-01-18 13:01:12,802 INFO  [http-bio-0.0.0.0-8080-exec-1] [org.nuxeo.runtime.reload.ReloadComponent] about to send flush
2016-01-18 13:01:12,834 WARN  [Quartz_Worker-1] [org.nuxeo.ecm.core.schema.SchemaManagerImpl] Schema base is redefined but will not be overridden
2016-01-18 13:01:12,849 INFO  [http-bio-0.0.0.0-8080-exec-1] [org.nuxeo.runtime.reload.ReloadComponent] returning from flush
2016-01-18 13:01:12,863 ERROR [ConnectDownloadThread-1-1] [org.nuxeo.connect.downloads.LocalDownloadingPackage] Package bchauvin-SANDBOX-0.0.0-SNAPSHOT is already installed

2016-01-18 12:59:48,561 WARN  [org.nuxeo.launcher.NuxeoLauncher] Server stopped.
2016-01-18 12:59:48,573 INFO  [org.nuxeo.launcher.config.ConfigurationGenerator] Configuration files generation (nuxeo.force.generation=true)...
2016-01-18 12:59:48,936 INFO  [org.nuxeo.launcher.config.ConfigurationGenerator] Configuration files generated.
2016-01-18 12:59:49,027 INFO  [org.nuxeo.launcher.connect.ConnectBroker] Relax mode changed from 'ask' to 'false' for executing the pending actions.
2016-01-18 13:00:08,694 INFO  [org.nuxeo.launcher.connect.ConnectBroker]
Dependency resolution:
  Installation order (1):        bchauvin-SANDBOX-0.0.0-SNAPSHOT
  Local packages to install (1): bchauvin-SANDBOX:0.0.0-SNAPSHOT

2016-01-18 13:00:08,698 INFO  [org.nuxeo.launcher.connect.ConnectBroker] Installing bchauvin-SANDBOX-0.0.0-SNAPSHOT
2016-01-18 13:00:08,733 INFO  [org.nuxeo.launcher.config.ServerConfigurator] Detected Tomcat server.
(...)
2016-01-18 13:00:09,891 WARN  [org.nuxeo.launcher.NuxeoLauncher] Server started with process ID 9402.
2016-01-18 13:00:09,891 INFO  [org.nuxeo.launcher.NuxeoLauncher] Go to http://localhost:8080/nuxeo