JCBC-265: Fixing ConfigurationProviderMock for unit test.

This changeset fixes the mock to not throw an unsupported
operation exception when reconfigure is called. This prevents
the unit test from executing correctly.

Change-Id: I6c6fe6c8f5e39fbf8680e90249b608f0a60880dd
Reviewed-on: http://review.couchbase.org/25101
Tested-by: Michael Nitschinger <michael.nitschinger@couchbase.com>
Reviewed-by: Michael Nitschinger <michael.nitschinger@couchbase.com>