Attempt to clean up tvolser dependencies

Attempt to clean up tvolser dependencies

The volserver only needs vl_errors.c to be locally generated, not
vlserver.h; in fact, the only consumers of vlserver.h in src/volser/
consume it via afs/vlserver.h.

Instead of reaching over to ../volser for the generated volerr.c,
generate our own local copy, as well as the volser.h generated from
the same error table -- volser.h is included with double-quotes from
the volser sources.

Add the appropriate dependencies on volser.h, and remove the unneeded
dependencies on vlserver.h

Change-Id: Ic6e728fa455419cc8e95dc25c41ed6d6b7d20934
Reviewed-on: http://gerrit.openafs.org/11380
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>