test/cases: increase api.sh gcp ssh connection timeout

Author: jrusz

test/cases/api/gcp.sh

@@ -183,7 +183,9 @@ function verify() {
   _instanceWaitSSH "$HOST"
 
   # Verify image
-  _ssh="$GCP_CMD compute ssh --strict-host-key-checking=no --ssh-key-file=$GCP_SSH_KEY --zone=$GCP_ZONE $SSH_USER@$GCP_INSTANCE_NAME --"
+  # Increase the timeout for ssh connection
+  SSH_FLAG='--ssh-flag=-o --ssh-flag=ConnectTimeout=600'
+  _ssh="$GCP_CMD compute ssh --strict-host-key-checking=no --ssh-key-file=$GCP_SSH_KEY --zone=$GCP_ZONE ${SSH_FLAG} $SSH_USER@$GCP_INSTANCE_NAME --"
 
   # TODO: remove this once el10 / c10s image moves to oslogin
   # On el10 / c10s, we need to ssh directly, because there is no "oslogin" feature