Added SIP NOTIFY check-sync support for remote reboot of endpoints

This should add check_sync support for remote reboot of endpoints, or config re-request for endpoints.

Tried compiling against master but there was a build error outside of my patch, so im submitting under the presumption that its fine.
It does - I was following other code snippets in order to get this to work, not knowing enough erlang on my own, sadly.  If its obvious to you what it needs to be changed to, would you mind going ahead and doing it? or do i have to since its my pull request?