CA-130987: Forward any exceptions thrown inside _snapshot

Signed-off-by: Vineeth Raveendran <vineeth.thampi@citrix.com>
Reviewed-by: Chandrika Srinivasan <chandrika.srinivasan@citrix.com>
Imported-by: Siddharth Vinothkumar <siddharth.vinothkumar@citrix.com>
Reviewed-by: Mate Lakat <mate.lakat@citrix.com>

(cherry picked from commit 6d7cf76dc400fbc4c8ccafddf72131c65724da67)

GitHub: closes #195 on xapi-project/sm