frameworks/C/lwan: Delete checkout directory if not fully installed
frameworks/C/lwan: Add MySQL test for Lwan benchmarks as well.
Merge pull request #1141 from lpereira/lwan-mysql

Add MySQL tests for Lwan
@hamiltont Dear Travis-CI, I love you.
Added the remaining tests.
Bumped Play version to 2.3.6.
Added HikariCP benchmark config.