parsemail: Handle duplicate comments more gracefully

Currently each time there is a comment with a duplicate msg-id, ADMINS
get an email with an exception.

Let's be more graceful and just debug log it.

Signed-off-by: Arkadiusz Hiler <arkadiusz.hiler@intel.com>
1 job for master in 1 minute and 11 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #144835
test

00:01:11