Catch more general exception in manager's create_volume

Catch more general exception in manager's create_volume

When fixing issues with inaccurate allocated_capacity tracking when
create_volume flow fails (Icd6b04ac60c17cbda225d3be8bcc4435ea0cd7a8)
it was ignored that drivers may raise all kinds of exceptions and these
aren't repacked into CinderException in the flow. This commit broadens
except clause to catch Exception when deciding if rescheduling
occurred while creating a volume. Also regression unit test is added.

Change-Id: I36058eacd1eb6b42c6a4311bd3382ddc9f47550c
Closes-Bug: 1438744