Fix resource-does-not-exist errors in tests.

[briandealwis]

Hit this exception when running tests localling. Probing the code, it seems WTP's Validation job releases the workspace lock, thus allowing our TestProject's delete to run and deleting the code from underneath the validation job. I'm not sure why the validation runs unprotected.

!ENTRY org.eclipse.wst.validation 4 0 2016-11-22 11:50:06.295
!MESSAGE Resource '/test0.7934389440457017' does not exist.
!STACK 1
org.eclipse.core.internal.resources.ResourceException: Resource '/test0.7934389440457017' does not exist.
	at org.eclipse.core.internal.resources.Resource.checkExists(Resource.java:334)
	at org.eclipse.core.internal.resources.Resource.checkAccessible(Resource.java:208)
	at org.eclipse.core.internal.resources.Project.checkAccessible(Project.java:140)
	at org.eclipse.core.internal.resources.Resource.accept(Resource.java:59)
	at org.eclipse.core.internal.resources.Resource.accept(Resource.java:51)
	at org.eclipse.wst.validation.internal.ValBuilderJob.fullBuild(ValBuilderJob.java:216)
	at org.eclipse.wst.validation.internal.ValBuilderJob.run(ValBuilderJob.java:178)
	at org.eclipse.wst.validation.internal.ValBuilderJob.runInWorkspace(ValBuilderJob.java:126)
	at org.eclipse.core.internal.resources.InternalWorkspaceJob.run(InternalWorkspaceJob.java:39)
	at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55)
!SUBENTRY 1 org.eclipse.core.resources 4 368 2016-11-22 11:50:06.295
!MESSAGE Resource '/test0.7934389440457017' does not exist.