KAFKA-13908 Rethrow ExecutionException to preserve original cause

[nizhikov]

Rethrow ExecutionException instead of wrapping it in RuntimeException. It will preserve original cause in method-wide catch block:

    } catch {
      case e: Throwable =>
        maybeChangeStatus(STARTING, STARTED)
        fatal("Fatal error during broker startup. Prepare to shutdown", e)
        shutdown()
        throw if (e.isInstanceOf[ExecutionException]) e.getCause else e
    }

Committer Checklist (excluded from commit message)

• [ ] Verify design and implementation
• [ ] Verify test coverage and CI build status
• [ ] Verify documentation (including upgrade notes)

[nizhikov]

Hello @showuon.

Can you, please, take a look at my changes?