t2004: standardize file naming in symlink test
t2004: standardize file naming in symlink test

Update "symlink" test to use the common file naming scheme so that its
temporary files can be cleaned up by the "rm -f path*" idiom employed by
other tests in this script.

Signed-off-by: Eric Sunshine <8d6e34f987851aa599257d3831a1af040886842f@sunshineco.com>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git