Fix test errors about WorkSchedulePath class initialization

java.lang.NoClassDefFoundError: Could not initialize class org.nuxeo.ecm.core.work.api.WorkSchedulePath
	at org.nuxeo.ecm.core.work.AbstractWork.getSchedulePath(AbstractWork.java:173)
	at org.nuxeo.ecm.core.work.AbstractWork.toString(AbstractWork.java:560)
	at java.lang.String.valueOf(String.java:2994)
	at java.lang.StringBuilder.append(StringBuilder.java:131)
	at org.nuxeo.ecm.core.work.WorkManagerImpl.scheduleAfterCommit(WorkManagerImpl.java:776)
	at org.nuxeo.ecm.core.work.WorkManagerImpl.schedule(WorkManagerImpl.java:718)
	at org.nuxeo.ecm.core.storage.sql.SessionImpl.scheduleWork(SessionImpl.java:357)
	at org.nuxeo.ecm.core.storage.sql.SessionImpl.flush(SessionImpl.java:345)
	at org.nuxeo.ecm.core.storage.sql.SessionImpl.save(SessionImpl.java:320)
	at org.nuxeo.ecm.core.storage.sql.ra.ConnectionImpl.save(ConnectionImpl.java:173)
	at org.nuxeo.ecm.core.storage.sql.coremodel.SQLSession.save(SQLSession.java:139)
	at org.nuxeo.ecm.core.api.AbstractSession.save(AbstractSession.java:1490)
	at org.nuxeo.ecm.platform.relations.CoreGraph$StatementAdder.run(CoreGraph.java:255)
	at org.nuxeo.ecm.core.api.UnrestrictedSessionRunner.runUnrestricted(UnrestrictedSessionRunner.java:135)
	at org.nuxeo.ecm.platform.relations.CoreGraph.add(CoreGraph.java:230)
	at org.nuxeo.ecm.platform.relations.TestCoreGraph.testAdd(TestCoreGraph.java:150)