CI: Run extra go linters
CI: Run extra go linters

Add the following golang linters to the static checks tool to avoid
such problems recurring:

- `staticcheck`
- `structcheck`
- `unused`

Fixes #988.

Signed-off-by: James O. D. Hunt <348fbaadfbada55ea105602bf5609e23ac1c4898@intel.com>

devimc/runtime,clearcontainers/runtime,devimc/runtime,chavafg/runtime,chavafg/runtime,clearcontainers/runtime