tests: call skip_test_ in place of echo+exit 77

tests: call skip_test_ in place of echo+exit 77

* tests/mv/no-target-dir: Likewise.
* tests/other-fs-tmpdir: Likewise.
* tests/rm/empty-name: Likewise.
* tests/rm/fail-eperm: Likewise.
* tests/rm/inaccessible: Likewise.
* tests/rm/isatty: Likewise.
* tests/rm/unreadable: Likewise.
* tests/setgid-check: Likewise.
* tests/sparse-file: Likewise.
* tests/strace: Likewise.
* tests/tail-2/append-only: Likewise.
* tests/tail-2/big-4gb: Likewise.
* tests/tail-2/tail-n0f: Likewise.
* tests/touch/dangling-symlink: Likewise.
* tests/touch/fifo: Likewise.
* tests/touch/not-owner: Likewise.
* tests/mv/i-3: Likewise.
* tests/umask-check: Likewise.
* tests/mv/acl: Likewise.
* tests/cp/acl: Likewise.
* tests/chgrp/deref: Likewise.
* tests/chmod/setgid: Likewise.
* tests/cp/existing-perm-race: Likewise.
* tests/cp/file-perm-race: Likewise.
* tests/cp/parent-perm-race: Likewise.
* tests/du/2g: Likewise.
* tests/du/8gb: Likewise.
* tests/du/long-from-unreadable: Likewise.
* tests/du/long-sloop: Likewise.
* tests/du/slink: Likewise.
* tests/ls/nameless-uid: Likewise.
* tests/ls/stat-dtype: Likewise.
* tests/misc/cat-proc: Likewise.
* tests/misc/md5sum-newline: Likewise.
* tests/misc/nice: Likewise.
* tests/misc/od-x8: Likewise.
* tests/misc/pwd-unreadable-parent: Likewise.
* tests/misc/selinux: Likewise.
* tests/misc/stty-row-col: Likewise.
* tests/misc/tac-continue: Likewise.
* tests/misc/arch: Likewise, and source $srcdir/../test-lib.sh *before*
the use of skip_test_.