Add a bit of coverage for varnishdm

bin/varnishtest/tests/u00012.vtc

@@ -14,7 +14,7 @@ client c1 {
 
 varnish v1 -vsl_catchup
 
-process p1 -log {varnishadm -p -n ${v1_name}} -start
+process p1 -log {varnishadm -t 12 -p -n ${v1_name}} -start
 
 # expect a full status line in pass mode (no banner)
 process p1 -write "ping\r"
@@ -28,3 +28,12 @@ process p1 -write "vcl.show vcl1\r"
 process p1 -expect-text 0 0 "backend s1"
 
 process p1 -screen_dump -write "\x04" -wait
+
+process p1 -log {varnishadm -t foobar 2>&1} -expect-exit 2 -run
+process p1 -expect-text 0 0 "-t: Invalid argument:"
+
+process p1 -log {varnishadm -Q 2>&1} -expect-exit 1 -run
+process p1 -expect-text 0 0 "Usage: varnishadm"
+
+process p2 -log {varnishadm -h 2>&1} -expect-exit 0 -run
+process p2 -expect-text 0 0 "Usage: varnishadm"