test: bump the container boot timeout when running w/o acceleration

test: bump the container boot timeout when running w/o acceleration

With plain QEMU on a saturated AWS region we might just barely miss the
timeout window, causing unexpected test fails:

[  688.681324] systemd-nspawn[1332]: [  OK  ] Finished systemd-user-sessions.service.
[  689.451267] systemd-nspawn[1332]: [  OK  ] Started console-getty.service.
[  689.572874] systemd-nspawn[1332]: [  OK  ] Reached target getty.target.
[  693.634609] testsuite-74.sh[1223]: + at_exit
[  693.634609] testsuite-74.sh[1223]: + rm -fv -- /tmp/test-dump /tmp/test-usr-dump /tmp/make-dump
[  693.838395] testsuite-74.sh[1502]: removed '/tmp/test-dump'
[  693.838395] testsuite-74.sh[1502]: removed '/tmp/test-usr-dump'
[  693.838395] testsuite-74.sh[1502]: removed '/tmp/make-dump'
[  693.951114] testsuite-74.sh[670]: + echo 'Subtest /usr/lib/systemd/tests/testdata/units/testsuite-74.coredump.sh failed'
[  693.951114] testsuite-74.sh[670]: Subtest /usr/lib/systemd/tests/testdata/units/testsuite-74.coredump.sh failed
[  693.951114] testsuite-74.sh[670]: + return 1
[  694.659094] systemd[1]: testsuite-74.service: Main process exited, code=exited, status=1/FAILURE
[  694.719563] systemd[1]: testsuite-74.service: Failed with result 'exit-code'.
[  694.882069] systemd[1]: Failed to start testsuite-74.service.
[  695.574445] systemd[1]: Reached target testsuite.target.
[  696.174844] systemd[1]: Starting end.service...
[  699.509408] systemd-nspawn[1332]:
[  699.509408] systemd-nspawn[1332]: CentOS Stream 9
[  699.509408] systemd-nspawn[1332]: Kernel 5.14.0-432.el9.x86_64 on an x86_64 (pts/0)
[  699.509408] systemd-nspawn[1332]:

Also, move the rest of container the setup for the user xattrs test into
the condition, since doing it without the actual test is pretty
pointless.