Refactor e-mail information saving into a single location

Review Request #8897 — Created April 12, 2017 and submitted — Latest diff uploaded

Information

Review Board
release-3.0.x

Reviewers

Each mail_{foo} function was saving review request and review
information identically in each function. It has now been refactored
into a single function that also ensures that only the relevant fields
are updated.

Ran unit tests.