src/kauth/krb_udp.c: Remove redundant NULL check for array address

src/kauth/krb_udp.c: Remove redundant NULL check for array address

Resolves this warning with clang:

krb_udp.c:302:13: warning: address of array 'tentry.misc_auth_bytes' will always evaluate to 'true' [-Wpointer-bool-conversion]
        if (tentry.misc_auth_bytes) {
        ~~  ~~~~~~~^~~~~~~~~~~~~~~

Change-Id: I0656b055090654eada2cd63476330fb288490acc
Reviewed-on: http://gerrit.openafs.org/11964
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>