Expand rendered image name to include sec and ms

Expand rendered image name to include sec and ms

Expand rendered image name to include seconds and milliseconds.
This reduces the probability of image name collisions on the cloud
from 1/60 to 1/60000.

The initial change Ic1853ba7566def397b8bce389e2779fe3020c7ce was
reverted, since the change had issues bringing up an instance on the
OpenStack cloud provider. This was because the default `instance_name`
value is taken as the `image_name`, when the instance_name is unset,
the instance_name does not allow FQDN format hostname ending with
a period+number.

The workaround is to use separate `instance_name` parameter in your
builder which does not end with period+number.

Fixed upstream in common-packer [1.].

[1.] https://gerrit.linuxfoundation.org/infra/#/c/10986/

JIRA: https://jira.linuxfoundation.org/browse/RELENG-971

Issue-ID: CIMAN-168
Change-Id: I451dd8956fbd2b97a47b5064d9802108f4fc3115
Signed-off-by: Anil Belur <abelur@linuxfoundation.org>