Update ViewOptions to correctly handle retrieving value from Enum types.
Update ViewOptions to correctly handle retrieving value from Enum types.

Motivation
==========
Allow users to pass in certain options that are Enums.

Modification
============
Change how Enum value is retrieved in ViewOptions.

Results
=======
All tests pass.

Change-Id: I344fbdc7f6326989fb1be433761308b66d6d4dcd
Reviewed-on: http://review.couchbase.org/c/couchbase-python-client/+/157549
Tested-by: Build Bot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: David Kelly <d83cd2a93a916ce0b0d4c1349b44be044799feca@gmail.com>

couchbase/couchbase-python-client,couchbase/couchbase-python-client