Pass correct param to gss_delete_sec_context

Thanks, clang!

Change-Id: Idecec836eb5821b54065fe6e909fe59143a3b95c
Refactor client-side GSS negotiation loop

Use a subroutine for the loop body, making memory management and
tracking of which variables are used where much cleaner.

Change-Id: I4a8f7922b2e1cc736a733959b11c8aa6a95924f6