Run tests as appropriate group

Need to add "groupadd" and "groupdel" for Alpine. See:

https://github.com/gliderlabs/docker-alpine/issues/326

test/test_nacm_credentials.sh

@@ -10,9 +10,6 @@
 # Magic line must be first in script (see README.md)
 s="$_" ; . ./lib.sh || if [ "$s" = $0 ]; then exit 0; else return 0; fi
 
-# Raw unit tester of backend unix socket.
-: ${clixon_util_socket:=$(which clixon_util_socket)}
-
 APPNAME=example
 
 # Common NACM scripts