[FIXED JENKINS-17667] - Syncronization of InstallerTranslator::getToolHome()

There appears to be some unthreadsafe initialization going on here.
Initialize/get inside a synchronized block for threadsaftey.
Merge pull request #1176 from jkolash/master

[FIXED JENKINS-17667] - Syncronization of InstallerTranslator::getToolHome()
Bundling the latest
[ZD-19640] diagnostic improvement in case impersonation failed.

I think this is an oversight in bded790f4651459b2ac41d9f96f2393204b41012. A random attacker wouldn't know the correct API token value,
so given that it matched, I think the caller should know that it was the impersonation that failed, not the authentication.

Also log this at a higher level, since this indicates a problem in SecurityRealm.