Fixed search to actually open the clicked folder

When a folder was clicked in a search, what was happening is the
refresh() in onStart() was being executed after onActivityResult(), so
the changeCurrentDir() executed in onActivityResult() was being
overriden by the refresh in onStart(). Since the mCurrentDir wasn't
being set until the NavigationTask ends, it would always go back to
the original directory. The change is to make the refresh not happen
if a NavigationTask is currently under way.

Change-Id: I5c354554c9b15fc9d14b4665852b40fb6a1f8853
Ticket: QRDL-932