RFR: Log warning on wrapped UncheckedRestExceptions

[Erik Joelsson]

In SKARA-1063, I introduced UncheckedRestException in order to avoid logging for errors that are very likely transient, and that are tracked with metrics as well. In some cases, specifically when running Jcheck in a bot, we end up wrapping that exception in a RuntimeException, which in turn causes us to log an error instead of warning. 

This patch tries to fix this by also checking nested exceptions in when catching RuntimeException in the BotRunner.

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Commit messages:
 - Log warning on wrapped UncheckedRestExceptions

Changes: https://git.openjdk.java.net/skara/pull/1292/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=1292&range=00
  Stats: 7 lines in 1 file changed: 6 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/skara/pull/1292.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/1292/head:pull/1292

PR: https://git.openjdk.java.net/skara/pull/1292