test_setup: Restart polkitd for rule to take effect

After some research, we found that polkit rule will take 1 second to
take effct after change. This will cause some fail cases if interval
between checking access and writing rule are short enough.

yumingfei pointed out restart polkit service will force rules to take
effect.

Signed-off-by: Hao Liu <hliu@redhat.com>
Merge pull request #1689 from Hao-Liu/fix_polkit

test_setup: Restart polkitd for rule to take effect