Fix cred cache detection
Fix cred cache detection

The stat call was not using the full path name, therefore it was always
failing.

Signed-off-by: Simo Sorce <65f99581a93cf30dafc32b5c178edc6b0294a07f@redhat.com>
Reviewed-by: Jan Pazdziora <5b16690b4000fd5ccfa8e89cc3062f7c650cdde2@redhat.com>
Close #91

frenche/mod_auth_gssapi,frenche/mod_auth_gssapi,frenche/mod_auth_gssapi,frenche/mod_auth_gssapi