Use get_secgroup_uuids in Instance

Instance._get_security_groups_id serves the same
purpose as neutron.get_secgroup_uuids. This change switches
Instance to using get_secgroup_uuids instead.

Updating the test has the side-effect on getting full test
coverage on get_secgroup_uuids, albeit indirectly.

Change-Id: I8cdc51692fd8d96e68c6c947891c9708f77d54c3
Related-Bug: #1250286
Add _() to fix i18N compliance (part 1)

In heat, almost 200 log message and at least 30 exception
message are not processed by _(), and will not been translated.
We should use '_("STRING ...")' to enable i18n support.

I will split to two parts for review easier because the files
lost of _() are too much.

Closes-Bug: #1249217

Change-Id: I2c86dc7770a7f6f107ba16711b9cba363ef9b906
Merge "Use get_secgroup_uuids in Instance"