[FaceRestTestutils.cc] Remove an unused paramter in _assertAddRecord().

The 1st paramter: JSONParserAgent *parser is not used as both input
and output. In addition, this patch also fixes a leak of a JSONParserAgent
instance stored in the variable.
Merge pull request #453 from project-hatohol/fix-test-face-rest-utils-add-record

[FaceRestTestutils.cc] Remove an unused paramter in _assertAddRecord().