constification of constifiable vars

[egernst]

From @egernst on February 22, 2018 23:22

Noticed that we pretty liberally use var ( ) for what could in many cases be treated as a const.
Example can be seen at https://github.com/containers/virtcontainers/blob/master/kata_agent.go#L38

Some of these are more explicitly marked as var since they are updated during unit tests (see *_test.go) to aid in testing. For the remainder it'd be a good idea to mark these as consts.

Copied from original issue: containers/virtcontainers#636