Concourse: run /usr/sbin/sshd in simple, consistent way

This is good for Ubuntu, CentOS, and SLES -- we shouldn't have needed to
change it
Signed-off-by: NGoutam Tadi <gtadi@pivotal.io>

concourse/scripts/setup_gpadmin_user.bash

@@ -91,13 +91,7 @@ setup_sshd() {
 
   setup_ssh_for_user root
 
-  # Test that sshd can start
-  if [ -x /etc/init.d/sshd ]; then
-    /etc/init.d/sshd start
-  elif [ -x /etc/init.d/ssh ]; then
-    # Ubuntu uses ssh instead of sshd
-    /etc/init.d/ssh start
-  fi
+  /usr/sbin/sshd
 
   ssh_keyscan_for_user root
   ssh_keyscan_for_user gpadmin