Add CentOS 7 support to hoist

[bonnyci[bot]]

Build failed.

• https://logs.bonnyci.org/check_github/BonnyCI/hoist/511/1505956030.15/bonnyci-run-check-multinode : FAILURE in 7m 52s

[SpamapS]

FYI, I did some squashes so it's at least a few less patches. No less daunting as a review task though. Sorry for that.

[bonnyci[bot]]

Build failed.

• https://logs.bonnyci.org/check_github/BonnyCI/hoist/511/1505969608.84/bonnyci-run-check-multinode : FAILURE in 1m 52s