test: don't redirect stdout/stderr to console

Turns out that redirecting a lot of output to the console can have some
funny effects, like random kernel soft lockups. I spotted this in
various CIs, but it remained almost entirely hidden thanks to
`softlockup_panic=1`, until 1a36d2672f which introduced a couple of
tests that log quite a lot in a short amount of time. This, in
combination with newer kernel version, which, for some reason, seem to
be more susceptible to such soft lockups, made the Arch Linux jobs soft
lockup quite a lot, see [0].

While debugging this I also noticed that runs which don't redirect
stdout/stderr to the console are noticeably faster, e.g.:

    # TEST-71 nspawn + QEMU (KVM), StandardOutput=journal+console
    Elapsed (wall clock) time (h:mm:ss or m:ss): 0:24.64
    # TEST-71 nspawn + QEMU (KVM), StandardOutput=journal
    Elapsed (wall clock) time (h:mm:ss or m:ss): 0:17.95

    # TEST-71 nspawn + QEMU, StandardOutput=journal+console
    Elapsed (wall clock) time (h:mm:ss or m:ss): 2:04.70
    # TEST-71 nspawn + QEMU, StandardOutput=journal
    Elapsed (wall clock) time (h:mm:ss or m:ss): 1:44.48

    # TEST-04 QEMU, StandardOutput=journal+console
    Elapsed (wall clock) time (h:mm:ss or m:ss): 4:22.70
    # TEST-04 QEMU, StandardOutput=console
    Elapsed (wall clock) time (h:mm:ss or m:ss): 5:04.67

Given all this, let's effectively revert ba7abf79a5, and dump the
testsuite-related journal messages only after the test finishes, so they
don't go through the slow console.

Resolves: systemd/systemd-centos-ci#660

[0] https://github.com/systemd/systemd-centos-ci/issues/660

test/test-functions

@@ -1032,7 +1032,6 @@ EOF
 DefaultEnvironment=${default_environment[*]}
 ManagerEnvironment=${manager_environment[*]}
 DefaultTimeoutStartSec=180s
-DefaultStandardOutput=journal+console
 EOF
 
     # ASAN and syscall filters aren't compatible with each other.
@@ -1785,10 +1784,10 @@ save_journal() {
         dest_name="system.journal"
     fi
 
-    if [[ -n "$TEST_SHOW_JOURNAL" ]]; then
+    # Show messages from the testsuite-XX.service or messages with priority "warning" and higher
-        echo "---- $source_dir ----"
+    echo " --- $source_dir ---"
-        "$JOURNALCTL" --no-pager -o short-monotonic --no-hostname --priority="$TEST_SHOW_JOURNAL" -D "$source_dir"
+    "$JOURNALCTL" --no-pager --no-hostname -o short-monotonic -D "$source_dir" \
-    fi
+        _SYSTEMD_UNIT="testsuite-${TESTID:?}.service" + PRIORITY=4 + PRIORITY=3 + PRIORITY=2 + PRIORITY=1 + PRIORITY=0
 
     if get_bool "$save"; then
         # If we don't have systemd-journal-remote copy all journals from /var/log/journal/
@@ -3339,18 +3338,6 @@ test_setup() {
             mask_supporting_services
         fi
 
-        # Send stdout/stderr of testsuite-*.service units to both journal and
-        # console to make debugging in CIs easier
-        # Note: we can't use a dropin for `testsuite-.service`, since that also
-        #       overrides 'sub-units' of some tests that already use a specific
-        #       value for Standard(Output|Error)=
-        #       (e.g. test/units/testsuite-66-deviceisolation.service)
-        if ! get_bool "$INTERACTIVE_DEBUG"; then
-            local dropin_dir="${initdir:?}/etc/systemd/system/testsuite-${TESTID:?}.service.d"
-            mkdir -p "$dropin_dir"
-            printf '[Service]\nStandardOutput=journal+console\nStandardError=journal+console' >"$dropin_dir/99-stdout.conf"
-        fi
-
         if get_bool "$IS_BUILT_WITH_COVERAGE"; then
             # Do an initial coverage capture, to make sure the final report includes
             # files that the tests didn't touch at all