Change gdb remote test support multi-request format.

The multi request-response test infrastructure support was adding
the optional request suffix iteration index as decimal but it needed
to be hex per spec.  This change fixes that.


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@209234 91177308-0d34-0410-b5e6-96231b3b80d8