Fix use-before-init in two test programs

If krb5_init_context fails, use a null context for getting the error
message, not a context we haven't yet initialized.  Observed by David
Benjamin <davidben@mit.edu> using clang.
Allocate space for NUL byte in test code

Caught by ASan.
Fix condition with empty body

Found by clang's warnings.

ticket: 7591 (new)
target_version: 1.11.2
tags: pullup
Fix kadmin_getpol format string

Commit 0780e46fc13dbafa177525164997cd204cc50b51 matched a %ld format
string with the integer 0, which is an int rather than a long.  Just
put 0 in the format string instead.  Noted by David Benjamin
<davidben@mit.edu>.
Fix argument type in kg_unseal_v1

The caller of kg_unseal_v1 passes a gss_qop_t * for the qop_state
parameter, so make it use that type instead of an int *.  Noted by
David Benjamin <davidben@mit.edu>.
Eliminate unused variables