Make recovery_target_action = pause work.

Previously even if recovery_target_action was set to pause and
the recovery target was reached, the recovery could never be paused.
Because the setting of pause was *always* overridden with that of
shutdown unexpectedly. This override is valid and intentional
if hot_standby is not enabled because there is no way to resume
the paused recovery in this case and the setting of pause is
completely useless. But not if hot_standby is enabled.

This patch changes the code so that the setting of pause is overridden
with that of shutdown only when hot_standby is not enabled.

Bug reported by Andres Freund

src/backend/access/transam/xlog.c

@@ -5141,7 +5141,7 @@ readRecoveryCommandFile(void)
 	 */
 	if (recoveryTargetAction == RECOVERY_TARGET_ACTION_PAUSE &&
 		recoveryTargetActionSet &&
-		standbyState == STANDBY_DISABLED)
+		!EnableHotStandby)
 		recoveryTargetAction = RECOVERY_TARGET_ACTION_SHUTDOWN;
 
 	/* Enable fetching from archive recovery area */