testsuite/xattrs: ignore SUNWattr_* in the Solaris xls helper

testsuite/xattrs: ignore SUNWattr_* in the Solaris xls helper

The Solaris xls() function listed every entry in the file's xattr
directory, which on Solaris includes OS-managed SUNWattr_ro and
SUNWattr_rw pseudo-attributes. SUNWattr_rw embeds the file creation
time, so its bytes naturally differ between the source and destination
files, making the xattrs and xattrs-hlink tests fail with diffs that
have nothing to do with rsync.

Rsync's own listxattr wrapper already filters these out
(lib/sysxattrs.c), so the right fix is to filter them in the test
display too. Other platforms are unaffected because each has its own
xls() branch in the case statement.

With the test now actually passing on Solaris, drop the CI hack that
overwrote testsuite/xattrs.test with a skip stub.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>