Fix sasl_list_mech_response_handler()
Fix sasl_list_mech_response_handler()

sasl_client_start() expects null-terminated string

Change-Id: Iee9e386f97d0abfa5ab0301373a71ca7c44db716
Reviewed-on: http://review.couchbase.org/12700
Tested-by: Sergey Avseyev <87f6d5e4fd3644c3c20800cde7fd3ad1569370b3@gmail.com>
Reviewed-by: Trond Norbye <60edd2ef23891a753f231b0c6f161dc634079a93@gmail.com>

couchbase/libcouchbase,couchbase/libcouchbase,mnunberg/libcouchbase,couchbase/libcouchbase,trondn/libcouchbase,trondn/libcouchbase,senthilkumaranb/libcouchbase,mody/libcouchbase,signmotion/libcouchbase,mnunberg/libcouchbase,signmotion/libcouchbase,mnunberg/libcouchbase,trondn/libcouchbase,couchbase/libcouchbase,uvenum/libcouchbase,trondn/libcouchbase,avsej/libcouchbase,kojiromike/libcouchbase,senthilkumaranb/libcouchbase,avsej/libcouchbase,maxim-ky/libcouchbase,signmotion/libcouchbase,couchbase/libcouchbase,avsej/libcouchbase,uvenum/libcouchbase,signmotion/libcouchbase,kojiromike/libcouchbase,senthilkumaranb/libcouchbase,mody/libcouchbase,trondn/libcouchbase,maxim-ky/libcouchbase,mody/libcouchbase,avsej/libcouchbase,uvenum/libcouchbase,kojiromike/libcouchbase,PureSwift/libcouchbase,PureSwift/libcouchbase,maxim-ky/libcouchbase,avsej/libcouchbase,avsej/libcouchbase,PureSwift/libcouchbase,senthilkumaranb/libcouchbase,maxim-ky/libcouchbase,PureSwift/libcouchbase,mnunberg/libcouchbase,couchbase/libcouchbase,mody/libcouchbase,couchbase/libcouchbase,mnunberg/libcouchbase,uvenum/libcouchbase,kojiromike/libcouchbase,avsej/libcouchbase,uvenum/libcouchbase