Webhook timeout

Our Gitlab instance needed the ability to increase the webhook_timeout used by HTTParty. It was hardcoded at 10 and I moved it to a gitlab.yaml file as a config variable

```
## Webhook settings
# webhook_timeout: 30 # default: 10 - Number of seconds to wait for HTTP response after sending webhook HTTP POST request

```
I had submitted the issue already and fixes #4954.  This is the rebase version of that commit.