Windows: Fix memory leak SRXAFSCB_GetCellServ

Windows: Fix memory leak SRXAFSCB_GetCellServ

In commit 19f1e0f7cf40c3da1d49c789358bd814f7e3b3eb strdup()
was replaced by xdr_alloc() and memcpy().  Unfortunately,
the patch was wrong and the pointer to which the result of
xdr_alloc() was assigned was overwritten with zero.

Change-Id: I0a9e6c03d67e2a1c811e84808fbbdd39f782ba87
Reviewed-on: http://gerrit.openafs.org/8162
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: Jeffrey Altman <jaltman@your-file-system.com>