Don't swallow PolicyNotAuthorized for resize/reboot actions

Removes 'except Exception' lines in the api which were preventing
PolicyNotAuthorized exceptions from bubbling up and returning 403 to the
caller.  This addresses policy exceptions in confirmResize,
revertResize, and reboot.

The try block calls into the compute api which sends a cast to perform
to bulk of the work, so there is little chance of an exception bubbling
up which is not already being caught.

Removes a unit test for a condition that should not exist.

Bug 1170453

Change-Id: I516a19894ab3d183057c774e84c4faa7053a6463
(cherry picked from commit 7e006ca39fc57e35244f471c0f0bb6773fdbbc28)
Merge "Don't swallow PolicyNotAuthorized for resize/reboot actions" into stable/grizzly