ghe-maintenance-mode-enable waits for writing processes to complete
ghe-maintenance-mode-enable waits for writing processes to complete

This polls the maintenance status admin API until all git, mysql,
and resque processes bleed out. This should really be on the
appliance side and implemented more sanely but we need to support
past versions. This code path is not used for versions post
11.10.340 since maintenance mode is not required for backups.

github/backup-utils,github/backup-utils,Teino1978-Corp/https-github.com-Teino1978-Corp-backup-utils,spotify/backup-utils