Remove similar check endpoints from GOCDB_monitor

[gregcorbett]

There are currently three such endpoints:

• ops_monitor_check.php: Which is the endpoint used by EGI Operations, returns a 500 status on an error, and accepts a fake_failure parameter to fake a failure.
• check.php: Used by internal monitoring, returns a 500 status on an error (post Add http response code to check.php #501)
• check_with_error.php: Always returns a php error code of 2, and a http status of 200.

I would suggest check_with_error.php is removed, and ops_monitor_check.php is coalesced into check.php (preserving the fake_failure behaviour).