Remove compile warning on ubuntu

config_parse_test.c: warning: the use of `mktemp' is dangerous,
                     better use `mkstemp' or `mkdtemp'

Change-Id: If4656ba38b4c3976316483d9e7b3b1946e5055e4
Reviewed-on: http://review.couchbase.org/42233
Tested-by: Trond Norbye <trond.norbye@gmail.com>
Reviewed-by: Dave Rigby <daver@couchbase.com>