[Core] When reseting a workspace, it must be up to date with origin

WorkspaceResourcesAdapterTest.testUploadResource() fails randomly.
The test uploads a resource file "file2.txt". Then it gets a workspace, and checks that the file is indeed present.
But sometimes it is not.
The problem is, that when getting a workspace from the pool, it gets cleared up but not aligned correctly on HEAD of the origin.
To reproduce the behaviour, put a breakpoint at:
com.nuxeo.studio.web.v2.wsadapter.WorkspaceResourcesAdapterTest.testUploadResource(), ligne 192 (

Workspace ws = workspaceService.getWorkspace(PROJECT);

)
Then delete all the workspaces from the cache which have the file:

$ find -name "file2.txt" |grep cat2
./myProject-#4-cloned-2016-06-24-14-15-28/studio/resources/cat2/file2.txt
./myProject-#2-cloned-2016-06-24-14-15-28/studio/resources/cat2/file2.txt

$ rm -rf myProject-#2-cloned-2016-06-24-14-15-28/ myProject-#4-cloned-2016-06-24-14-15-28/

Then continue the test execution.