email-test-patchset: grab all To and Cc headers.

email-test-patchset: grab all To and Cc headers.

This change modifies email-test-patchset to grab every To and Cc header
instead of just the first. Because refernces to to and cc except email
lists (comma seperated), we use merge_addresses with an empty second
parameter. This works due to recent changes to the merge_addresses
function see in a previous patch in this series.

Artem: amend the patch a tiny bit.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>