JSCBC-698: Fixed issue with MutateIn placeholders.
JSCBC-698: Fixed issue with MutateIn placeholders.

Motivation
----------
MutateIn supports using placeholders for inserting server
generated information such as the CAS.  Due to an implementation
detail this was not working.

CHanges
-------
Moved JSON transcoding of the values for MutateIn after the check
to see if it is a placeholder.

Change-Id: I964be0f2710d35d8b7ac7cd7da48a92766f8ad20
Reviewed-on: http://review.couchbase.org/c/couchnode/+/130444
Reviewed-by: David Kelly <d83cd2a93a916ce0b0d4c1349b44be044799feca@gmail.com>
Reviewed-by: Charles Dixon <e13bf4498b4994e133fd3586350658dc4a59329a@gmail.com>
Tested-by: Brett Lawson <c8c4369773d7d7226e031f0c4af62e3f38a08510@gmail.com>

brett19/couchnode,couchbase/couchnode,brett19/couchnode,couchbase/couchnode,couchbase/couchnode,couchbase/couchnode,brett19/couchnode