Just stop trying to make Cassandane work on s390x.

cyrus-imapd.spec

@@ -406,6 +406,17 @@ make %{?_smp_mflags} check || exit 1
 exit 0
 %endif
 
+%ifarch s390x
+# Unfortunately s390x is simply too slow to reliably run the test suite right
+# now.  The suite brings up and tears down a complete cyrus environment for
+# each test, and the builders are simply unable to handle this reliably right
+# now.  Tests will simply fail randomly, and playing whack-a-mole with every
+# potential failure when a build takes seven hours is just too much.
+# s390x-specific test information is still present below in case situation
+# improves.
+exit 0
+%endif
+
 # Run the Cassandane test suite.  This will exhaustively test the various
 # server components, but running it in a mock chroot is rather an exercise.
 # Sadly Cassandane simply can't run on a 32-bit host at the moment.  It needs
@@ -635,6 +646,8 @@ getent passwd cyrus >/dev/null || /usr/sbin/useradd -c "Cyrus IMAP Server" -d /v
   complete a single test in 20 seconds.
 - Disable the Metronome tests; upstream says that they just won't reliably on
   shared hardware.
+- Don't bother running Cassandane on s390x for now.  The machines are simply
+  too slow.
 
 * Tue Jun 06 2017 Jitka Plesnikova <jplesnik@redhat.com> - 3.0.1-4
 - Perl 5.26 rebuild