Merge branch 'lsfd--fix-2691' of https://github.com/masatake/util-linux

Merge branch 'lsfd--fix-2691' of https://github.com/masatake/util-linux

* 'lsfd--fix-2691' of https://github.com/masatake/util-linux:
  tests: (lsfd::column-xmode) skip some subtests if OFD locks are not available
  tests: (lsfd) skip mkfds-netns if SIOCGSKNS is not defined
  tests: (lsfd) add lsfd_check_mkfds_factory as a help function
  tests: (test_mkfds) add --is-available option
  lsfd: build lsfd even if kcmp.h is not available
  tests: (refactor (test_mkfds, lsfd)) use TS_EXIT_NOTSUPP instead of EXIT_ENOSYS