Windows: revise NTSTATUS response for ALLBUSY, ALLOFFLINE, and ALLDOWN

Windows: revise NTSTATUS response for ALLBUSY, ALLOFFLINE, and ALLDOWN

Replace STATUS_IO_TIMEOUT with RPC_NT_SERVER_TOO_BUSY for CM_ERROR_ALLBUSY.

Replace STATUS_PATH_NOT_FOUND with RPC_NT_SERVER_UNAVAILABLE for
CM_ERROR_ALLOFFLINE and CM_ERROR_ALLBUSY.

These errors provide a more meaningful message to end users when
a failure occurs.

LICENSE MIT

Change-Id: I34483f8f696285477fa0f8a8dac3b0ff33dee6b4
Reviewed-on: http://gerrit.openafs.org/2663
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: Jeffrey Altman <jaltman@openafs.org>