Apply EM_COINC to superevent and external event in parallel
The Sentry error (https://sentry.io/organizations/ligo-caltech/issues/1161891996/?environment=production&environment=playground&query=is%3Aunresolved, at least part of the cases of it) has led to external events after the first to fail to have the EM_COINC
label apply to them. This change is to apply EM_COINC
to the superevent and external event asynchronously so that one failing does not block the other.
Edited by Brandon Piotrzkowski