The .cnf files can have valueless options present.
This commit ensures that these valueless options are not ignored
Addtionally, my.cnf overrides are added to the variable overrides
test file to ensure that the my.cnf file can run through the
config_template engine properly.
Change-Id: I8b09c2520c84bb43353b4c56bac157259f71b041
Closes-Bug: #1693234