Fix ntpd start on centos in cloud-init boothook

1) Add forgottent ntpd start into centos's cloud-init boothook.

2) Toggle ntp server on ubuntu to be sure it will start with correct
settings.

3) Fix typo in both boothook files
ntp(d) must be stopped before syncing date with ntpdate.

Change-Id: I4e8e912b61a57c84e24e13be10983654bcfec0ab
Closes-Bug: #1394617
Merge "Fix ntpd start on centos in cloud-init boothook"