RAVEN log fix to specify both GW and Ext events

Closes #908 (closed). This MR allows RAVEN to now post a log message containing both the GW event and External event in the log message when we are waiting for both the sky maps.

changed milestone to %GWCelery 2.6.1 release

added External Triggers Logging Sky Maps labels

assigned to @gaurav.waratkar

requested review from @brandon.piotrzkowski

approved this merge request

merged

mentioned in issue #908 (closed)