CA-122205: Resolve race between VDI.activate and GC.

The issue here is journaler._getAllEntries() that activates, opens and
deactivates journaler tagged LV files from the LVHDSR.attach
call. A parallel running GC could remove the journaler LV during this
time, resulting in _getAllEntries to throw an exception EIO. Ignoring
such errors in such cases, since it reduces the false positives.

Signed-off-by: Siddharth Vinothkumar <siddharth.vinothkumar@citrix.com>
Reviewed-by: Vineeth Thampi Raveendran <vineeth.thampi@citrix.com>
Reviewed-by: Thomas Sanders <thomas.sanders@citrix.com>

GitHub: closes #81 on xapi-project/sm