Simplify rsync install
Simplify rsync install

For some reason, tce-load exits with an error even after a successful
install of rsync. Therefore, manually recheck if the install worked,
and if it didn’t, fall back to installing via the pre-built rsync
binary in the GitHub repo.

interactive-pioneers/docker-osx-dev,yoanisgil/docker-osx-dev,ejones/docker-osx-dev,devotox/docker-osx-dev,brikis98/docker-osx-dev,styleseat/docker-osx-dev