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.
The *_maintenance functions should take care of converting types, if necessary, before calling the underlying functions. In this case, `ecallmgr_fs_notify:check_sync/2` should only accept `ne_binary()` arguments, with the `ecallmgr_maintenance:check_sync/2` ensuring the args are binaries before calling into `ecallmgr_fs_notify`. Does that make sense?