Windows: cm_BPlusDirIsEmpty

Provide a function to determine if a directory is empty or not.

Reviewed-on: http://gerrit.openafs.org/9777
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
(cherry picked from commit 5e8bfcb42cbb3652238fec2dbe1c1d65bc2c1ccd)

Change-Id: I3d71df833104c4dc049b737a593224657453ccfd
Reviewed-on: http://gerrit.openafs.org/9811
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Windows: cm_MapRPCErrorRmdir EEXIST == ENOTEMPTY

If the file server is asked to remove a directory that is not empty
one might expect it to return UAENOTEMPTY but instead it returns UAEEXIST.

The error translation function cm_MapRPCErrorRmdir did not include
EEXIST in the list of errors that convert to CM_ERROR_NOTEMPTY.

Prior to IBM AFS 3.5 the file server did return ENOTEMPTY and if a
particular platform did not define ENOTEMPTY, ENOTEMPTY was defined to
be EEXIST.  To late to change things back now.

Reviewed-on: http://gerrit.openafs.org/9778
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
(cherry picked from commit 6c73b8350a4bc67db271a5294c5fdf1e51e9033a)

Change-Id: I81f11638e1105371d4c70840e8902773e4a9a84a
Reviewed-on: http://gerrit.openafs.org/9812
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>