tests: use killdaemons in hgweb tests

hgweb tests often failed on my system because the serve port wasn't free when a
new hgweb was started; the killed hg wasn't completely dead yet.

Now we use killdaemons which waits for the process to die.

tests/test-hgweb

@@ -31,7 +31,7 b' echo % should give a 404 - file does not'
 "$TESTDIR/get-with-headers.py" localhost:$HGPORT '/diff/tip/bork?style=raw'
 
 echo % stop and restart
-kill `cat hg.pid`
+"$TESTDIR/killdaemons.py"
 hg serve -p $HGPORT -d --pid-file=hg.pid -A access.log
 cat hg.pid >> $DAEMON_PIDS
 # Test the access/error files are opened in append mode

tests/test-hgweb-diffs

@@ -20,7 +20,7 b' echo % diff removed file'
 "$TESTDIR/get-with-headers.py" localhost:$HGPORT '/diff/tip/a'
 
 echo % set up hgweb with git diffs
-kill `cat hg.pid`
+"$TESTDIR/killdaemons.py"
 hg serve --config 'diff.git=1' -n test -p $HGPORT -d --pid-file=hg.pid -A access.log -E errors.log
 cat hg.pid >> $DAEMON_PIDS