race condition in Logger rotation can cause unexpected errors

[davidnich]

ex:

logging error: System exception: /Users/david/src/Qorus/test/qlib/Logger.qm:1724 (Qore): FILE-WRITE-ERROR: file has not been opened
  File::print() called at /Users/david/src/Qorus/test/qlib/Logger.qm:1724 (Qore builtin code)
  LoggerAppenderFile::processEventImpl() called at /Users/david/src/Qorus/test/qlib/Logger.qm:1997 (Qore user code)
  LoggerAppenderFileRotate::processEventImpl() called at /Users/david/src/Qorus/test/qlib/Logger.qm:1196 (Qore user code)
  LoggerAppender::processEvent() called at /Users/david/src/Qorus/test/qlib/Logger.qm:1146 (Qore user code)
  LoggerAppender::pushEvent() called at /Users/david/src/Qorus/test/qlib/Logger.qm:1182 (Qore user code)
  LoggerAppender::post() called at /Users/david/src/Qorus/test/qlib/Logger.qm:3357 (Qore user code)
  Logger::callAppenders() called at /Users/david/src/Qorus/test/qlib/Logger.qm:3426 (Qore user code)
  Logger::logIntern() called at /Users/david/src/Qorus/test/qlib/Logger.qm:3476 (Qore user code)
  Logger::log() called at qdsp:421 (Qore user code)
  QDsp::logArgs() called at AbstractLogger.qc:212 (Qore user code)
  AbstractLogger::error() called at qdsp:410 (Qore user code)
  QDsp::processCmdImpl() called at AbstractQorusDistributedProcess.qc:426 (Qore user code)
  AbstractQorusDistributedProcess::processCmd() called at AbstractQorusDistributedProcess.qc:382 (Qore user code)
  AbstractQorusDistributedProcess::handleRouterMsg() called at AbstractQorusClientProcess.qc:1041 (Qore user code)
  AbstractQorusClientProcess::startBackgroundIntern() called at AbstractQorusClientProcess.qc:187 (Qore user code)
  *** thread started by background operator ***
log msg was: "exception handling cmd: \"ROTATE_LOGGER\" from sender: \"qorus-qdsp-omq-34164ae43dd624e042ca63240b6c6c09276a9e20-client-512-4\" \"x\": /Users/david/src/Qorus/test/qlib/Logger.qm:1992 (Qore): RENAME-ERROR: rename('/Users/david/src/Qorus/test/log/OMQ-harpoon-1-QDSP-omq.log', '/Users/david/src/Qorus/test/log/OMQ-harpoon-1-QDSP-omq.log.1') failed: No such file or directory"