logger: Display timezone as offset
logger: Display timezone as offset

Change format of time included in log entries to display the timezone
as an offset.

Example of old format:

    time="2017-09-28 13:22:58.965483966 +0100 BST"

Example of new format:

    time="2017-09-29T13:22:58.965483966+01:00"

Fixes #650.

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

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