test: trigger new events after all currently queued events are processed

Otherwise, udevd may be busy and udevadm may not receive the reply
for the control packet within the time limit.

test/units/testsuite-17.10.sh

@@ -87,6 +87,7 @@ assert_rc 124 timeout 5 udevadm monitor -t systemd
 assert_rc 124 timeout 5 udevadm monitor --tag-match hello
 udevadm monitor -h
 
+udevadm settle
 udevadm settle -t 5
 udevadm settle -E /sys/class/net/$netdev
 udevadm settle -h
@@ -193,7 +194,9 @@ udevadm trigger --initialized-match
 udevadm trigger --initialized-nomatch
 udevadm trigger -w
 udevadm trigger --uuid /sys/class/net/$netdev
+udevadm settle -t 300
 udevadm trigger --wait-daemon
+udevadm settle -t 300
 udevadm trigger --wait-daemon=5
 udevadm trigger -h