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.
#!/bin/sh
# a test for issue586
hg init a
cd a
echo a > a
hg ci -Ama
hg init ../b
cd ../b
echo b > b
hg ci -Amb
hg pull -f ../a
hg merge
hg rm -f a
hg ci -Amc
hg st -A