This reduces the amount of sleep time to speed up testing.

master:
PASS
ok  	github.com/coredns/coredns/test	42.088s
12,33s user 1,30s system 44,29s elapsed 30%CPU ()

this branch:
PASS
ok  	github.com/coredns/coredns/test	33.527s
Signed-off-by: Miek Gieben <miek@miek.nl>