(PUP-2399) Add mailalias acceptance tests

Add basic acceptance tests for mailalias type. This adds acceptance
tests for create, query, modify, and destroy.

The tests assume that the mailalias type manages the default
/etc/aliases text file as well as updating the binary database
that the aliases file is the source for.
(PUP-2399) Remove testing of newaliases

As per PUP-1143, the mailalias type does not manage the state of
the aliases.db file via 'newaliases', 'sendmail -bi', or any other
mechanism due to compatibility issues. Since this is the case,
all testing of the aliases.db file have been removed from the
mailaliases tests in this commit.
Merge pull request #2599 from johnduarte/pup-2399-mailalias-acceptance

(PUP-2399) Add mailalias acceptance tests