tests: refactor more tests to use mkfifo_or_skip_
* tests/cp/existing-perm-race: s/mkfifo/mkfifo_or_skip_/
* tests/cp/file-perm-race: Likewise.
* tests/cp/parent-perm-race: Likewise.
* tests/cp/special-f: Likewise.
* tests/dd/reblock: Likewise.
* tests/ls/file-type: Likewise.
* tests/misc/cat-buf: Likewise.
* tests/misc/mknod: Likewise.
* tests/misc/printf-surprise: Likewise.
* tests/misc/selinux: Likewise.
* tests/misc/sort-spinlock-abuse: Likewise.
* tests/misc/stdbuf: Likewise.
* tests/misc/tac-continue: Likewise.
* tests/init.cfg: Improve the error message when skipping.
14 files changed: