Make sure the default ec2_group egress rule is not removed

Upon a second run, the default egress rule will be removed when a
vpc is specified but no other egress rules were set. This patch
corrects that behavior by removing the default egress rule from the
list of unmatched outbound rules.

Fixes #7309
Use the existing module_vars during the templating of module_vars

Since some of the vars contained in there may be used in the templating
of other variables. This also reverts e83a494 which originally fixed
issue #6979 but broke some other variable related things.

Fixes #6979
Fixes #7321
Fixes #7332