Make support for nscd flushing optional

[keszybz]

Fedora will deprecate support for nscd in the upcoming release [1] and plans to
drop it in the next one [2]. At that point we might as well build systemd
without that support too, since there'll be nothing to talk too.

[1] https://fedoraproject.org/wiki/Changes/DeprecateNSCD
[2] https://fedoraproject.org/wiki/Changes/RemoveNSCD

[bluca]

bionic-i386 timed out as usual. Error in TEST-02-UNITTESTS on CentOS is unrelated too, although slightly worrying:

08:13:14 --- test-journal-flush begin ---
08:13:14 journal_file_copy_entry failed: Bad message
08:13:14 Assertion 'r >= 0' failed at src/journal/test-journal-flush.c:52, function main(). Aborting.

maybe a bad disk write? Paging @mrc0mmand

[mrc0mmand]

bionic-i386 timed out as usual. Error in TEST-02-UNITTESTS on CentOS is unrelated too, although slightly worrying:

08:13:14 --- test-journal-flush begin ---
08:13:14 journal_file_copy_entry failed: Bad message
08:13:14 Assertion 'r >= 0' failed at src/journal/test-journal-flush.c:52, function main(). Aborting.

maybe a bad disk write? Paging @mrc0mmand

I noticed that too in several cases over the past several days and it's indeed worrying, since it's failing in the CentOS 7 job (i.e. without nested KVM, just regular KVM). I'm not sure if anything has changed in the journal stuff to cause this though...