Checkable: Use correct timeout for rescheduling remote checks

Previously, the `command#timeout` which by default is `1m`, was used to reschedule
the just sent remote check. However, this results into a bunch of extra checks being
sent to the remote host, even though the first one is still running. That's because
if one want to override the default timeout of the command for a specific host/service,
one has to set the `checkable#check_timeout` attribute to the desired value. So, this
commit makes sure that the `checkable#check_timeout` attribute (if set) is used to
reschedule the remote check.

Author: yhabteab

lib/icinga/checkable-check.cpp

@@ -624,12 +624,16 @@ void Checkable::ExecuteCheck()
 			if (service)
 				params->Set("service", service->GetShortName());
 
+			double checkTimeout = GetCheckCommand()->GetTimeout();
+
 			/*
 			 * If the host/service object specifies the 'check_timeout' attribute,
 			 * forward this to the remote endpoint to limit the command execution time.
 			 */
-			if (!GetCheckTimeout().IsEmpty())
-				params->Set("check_timeout", GetCheckTimeout());
+			if (auto ckCheckTimeout(GetCheckTimeout()); !ckCheckTimeout.IsEmpty()) {
+				checkTimeout = Convert::ToDouble(ckCheckTimeout);
+				params->Set("check_timeout", ckCheckTimeout);
+			}
 
 			params->Set("macros", macros);
 
@@ -642,7 +646,7 @@ void Checkable::ExecuteCheck()
 			 * a check result from the remote instance. The check will be re-scheduled
 			 * using the proper check interval once we've received a check result.
 			 */
-			SetNextCheck(Utility::GetTime() + GetCheckCommand()->GetTimeout() + 30);
+			SetNextCheck(Utility::GetTime() + checkTimeout + 30);
 
 		/*
 		 * Let the user know that there was a problem with the check if