Add --no-process-group flag to smbd (#147)

Latest Samba on Alpine fails with "Failed to create session" without
this flag.

samba.sh

@@ -255,5 +255,5 @@ elif ps -ef | egrep -v grep | grep -q smbd; then
     echo "Service already running, please restart container to apply changes"
 else
     [[ ${NMBD:-""} ]] && ionice -c 3 nmbd -D
-    exec ionice -c 3 smbd -FS </dev/null
-fi
+    exec ionice -c 3 smbd -FS --no-process-group </dev/null
+fi