Patch and simplify percona-server formulae

[bbergstrom]

Description

Fix some bugs in the keg only formulas. Rename them to simplify configuration for mysqld_multi and apps using non-default version.
Remove extraneous linked percona-server57 formula.

QA

Note, it shouldn't happen, but this has the risk of losing your existing mysql data directory.

Prep

brew tap --full sportngin/homebrew
cd /usr/local/Library/Taps/sportngin/homebrew-homebrew/
git pull
git checkout multi

Tests

brew install sportngin/homebrew/percona-server55
brew install sportngin/homebrew/percona-server57
brew uninstall sportngin/homebrew/percona-server55 && brew uninstall sportngin/homebrew/percona-server57

Reset

cd /usr/local/Library/Taps/sportngin/homebrew-homebrew/
git checkout master

[anfleene]

==> Installing percona-server57 from sportngin/homebrew
==> Downloading https://s3.amazonaws.com/sportngin-homebrew-bottles/percona-server57-5.7.11-4.el_capitan.bottle.1.tar.gz
######################################################################## 100.0%
Error: SHA256 mismatch
Expected: c395062a832012b1c0aea7cbf922f0d3d3cd40f3f2b01de5e829a05b4f321871
Actual: 8598ac79a071c423130b99a9793dd67bab7b9d373c9697ae72c8a98449ef4273
Archive: /Library/Caches/Homebrew/percona-server57-5.7.11-4.el_capitan.bottle.1.tar.gz
To retry an incomplete download, remove the file above.
Warning: Bottle installation failed: building from source.

[anfleene]

QA passes 👍