Fix docimpact bug generation code

My sincere apologies to the infra team.

The original code to create bugs from DocImpact itself suffered
from a bug - it was trying to refer to an email address rather than
an impact line. Luckily, due to the design, this had no impact on
 sending Impact emails for security or docs.

This change correctly checks for docimpact prior to bug creation.

Change-Id: I1b8e037cab0a0424c765706f4a7b690ba5bd96d0
Reviewed-on: https://review.openstack.org/32994
Reviewed-by: Diane Fleming <diane.fleming@rackspace.com>
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Reviewed-by: Khai Do <zaro0508@gmail.com>
Approved: James E. Blair <corvus@inaugust.com>
Reviewed-by: James E. Blair <corvus@inaugust.com>
Tested-by: Jenkins