Don't print echobot link when disabling mail

- On a fresh install, if cmdeploy is run the first time with the
  --disable-mail option, the echobot invite-link.txt file will not
  exist yet.
- Only print the echobot invite link if --disable-mail was not
  specified.  This fixes the fresh-install error case, and also makes
  sense when disabling mail in general, because the echo bot will not
  be available at that time.

cmdeploy/src/cmdeploy/cmdeploy.py

@@ -109,6 +109,7 @@ def run_cmd(args, out):
     try:
         retcode = out.check_call(cmd, env=env)
         if retcode == 0:
+            if not args.disable_mail:
                 print("\nYou can try out the relay by talking to this echo bot: ")
                 sshexec = SSHExec(args.config.mail_domain, verbose=args.verbose)
                 print(