import: skip sockets and fifos when creating archives

import: skip sockets and fifos when creating archives

Fixes #40239.

$ SYSTEMD_LOG_LEVEL=debug SYSTEMD_LOG_LOCATION=1 build/test-tar -c /var/tmp/tar1.tar /var/tmp/with-fifo/
src/basic/dlfcn-util.c:66: Loaded shared library 'libarchive.so.13' via dlopen().
src/shared/tar-util.c:1422: Archiving '.'...
src/basic/dlfcn-util.c:66: Loaded shared library 'libacl.so.1' via dlopen().
src/shared/tar-util.c:1152: Skipping './fifo' (fifo).
src/shared/tar-util.c:1152: Skipping './unix' (sock).