Disable ProcessStartupPacket fault injector for FTS handler process

This was found in the dispatch ICG regress test where
ProcessStartupPacket fault injector was being used. In this recent
version of 6.0, FTS probe handler now uses ProcessStartupPacket. In
addition to blocking the backend, this now blocks the FTS probe
handler which caused failover to occur.

Author: Xin Zhang <xzhang@pivotal.io>
Author: Jimmy Yih <jyih@pivotal.io>

src/backend/postmaster/postmaster.c

@@ -2841,7 +2841,10 @@ retry1:
 			break;
 	}
 
-	SIMPLE_FAULT_INJECTOR(ProcessStartupPacketFault);
+	if (!am_ftshandler)
+	{
+		SIMPLE_FAULT_INJECTOR(ProcessStartupPacketFault);
+	}
 
 	return STATUS_OK;
 }