Avoid calling krb5_free_context(NULL)
Several places in the code currently call krb5_free_context(ctx) in a
cleanup code path, where 'ctx' may or may not be NULL. This is not
guaranteed to be okay, so check for NULL to make sure we don't cause
issues in these code paths.
While we are here cleaning up krb5_free_context() calls, also fix a
few call sites in afscp_util.c that were not calling krb5_free_context
in all error paths.
Change-Id: I881f01bdf94f00079f84c4bd4bcfa58998e51ac9
Reviewed-on: https://gerrit.openafs.org/13461
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>