Deorbit separate JUAFS build

Since 80943970b8cfcdf3fc630b25804aebaea228bd73, when the web enhancements
were enabled universally, there has no longer been a functional difference
between the UAFS and JUAFS builds.  Their object files are compiled
using the same compilation rule, and the list of object files differed
only by rx_kmutex.o (which is devoid of content) and xdr_int32.o
(which is preumably an oversight).

Save the extra build time by just reinstalling libuafs.a as libjuafs.a
to preserve the existing interfaces.

Additionally, drop the LIBJUAFS make variable -- all definitions set
it to libjuafs.a.  Similarly, the LIBJUAFS_FLAGS variable was unused
and can be removed.

Change-Id: I2074d5bc26e326db36b16e055431818ef1c69210
Reviewed-on: http://gerrit.openafs.org/11471
Reviewed-by: D Brashear <shadow@your-file-system.com>
Tested-by: D Brashear <shadow@your-file-system.com>