clang-16: Fix conditionally unused-but-set variables

clang-16: Fix conditionally unused-but-set variables

clang-16 is flagging unused-but-set variables which result in build
errors when --enable-warning is turned on.

   remote.c:485:15: error: variable 'pass' set but not used
       [-Werror,-Wunused-but-set-variable]
     afs_int32 pass;
              ^
These variables are actually used in specific cases depending on
build configuration (e.g. AFS_PTHREAD_ENV, etc.).

Relocate these variables so they are fully defined or referenced within
preprocessor '#if' blocks.

Change-Id: I900a192ec781be4ab4453769e1d8f0cc48fe5757
Reviewed-on: https://gerrit.openafs.org/15177
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: BuildBot <buildbot@rampaginggeek.com>