Revert secret path

Secret path submitted in ced39bcd
was incorrect and is being reverted. Docker Swarm by default
stores its sercrets in /run/secrets.

Signed-off-by: Alex Ellis (VMware) <alexellis2@gmail.com>

docker-compose.yml

@@ -17,7 +17,7 @@ services:
             direct_functions: "true"    # Functions are invoked directly over the overlay network
             direct_functions_suffix: ""
             basic_auth: "false"
-            secret_mount_path: "/var/openfaas/secrets/"
+            secret_mount_path: "/run/secrets/"
         deploy:
             resources:
                 # limits:   # Enable if you want to limit memory usage