Merge pull request #23 from tmakatos/master

CP-4614: Fix syntax error.
CA-107572: Ignore UUID not found exception during SR scan

VM migration failed because XAPI throw VDI UUID not found exception.
The VDI was already removed, the fix will catch the exception and discard it.

Signed-off-by: Sisimon Soman <sisimon.soman@citrix.com>
Acked-by: Thanos Makatos <thanos.makatos@citrix.com

GitHub: closes #17 on xapi-project/sm
CA-102329: VDI.delete: avoid duplicate GC restarts

In VDI.delete, there is a race condition where two threads attempt to
re-start a running GC/coalesce daemon, because re-starting the
GC/coalesce is done by blindly writing a value to a file (see IPC.py).
If one thread finds that there is re-start pending, there's no need to
issue another GC/coalesce re-start.

Signed-off-by: Thanos Makatos <thanos.makatos@citrix.com>
Acked-by: Zheng Li <zheng.li@citrix.com>

GitHub: closes #8 on xapi-project/sm