Fixed all JFace errors encountered on my fedora 24.
testRefreshWithAddedChildren: GTK3 processes adding new children a
slower than GTK2. Using a waitForJobs() call gets the correct assertion.
testExpandToLevel: Similar issue as above, but solved using a
processEvents() that was missing.

Change-Id: Ia6245ce2984ad6d1731a7db45467465ba6c31f57
Signed-off-by: Ian Pun <ipun@redhat.com>