Fix handling of serialized data in filtering of volumes

Commit 4aaf40ba1aab4d7c347b05750d0fe21f8d1bcc68 has introduced a bug.
'ast.literal_eval(v)' throws exception 'SyntaxError' if 'v' is an expression
such as UUID '920da701-93c1-4178-9f1a-ef1c7a8a384d', 'd-', or 'd+'.
Catch the 'SyntaxError' exception in addition to 'ValueError' and
assume 'v' is a string. So the API can handle the request successfully
rather than returning a '500' error code.

Change-Id: Ib50cf3be41ae96ed1f9ef0463ced71443e59061c
Closes-Bug: #1406504
Merge "Fix handling of serialized data in filtering of volumes"