[krbdev.mit.edu #7805] Potential leaks in error paths in acquire_accept_cred

[Andrea Campi via RT]

The error handling if() blocks at lines 227 and 234
of src/lib/gssapi/krb5/acquire_cred.c are missing krb5_kt_close(context,
kt);

I don't have a test case, but we noticed while debugging a similar problem.