Adds more integration tests

[claudiubelu]

Adds coverage for minion pool power cycling, exercising PowerOnMinionMachineTask / PowerOffMinionMachineTask and
_set_minion_machine_power_status. These were previously uncovered since existing pool tests never scale a pool beyond its minimum size.

Adds new tests configures pools with the "poweroff" retention strategy and a tiny idle time, then runs two separate transfers concurrently. The second execution allocates a new minion, scaling the pool beyond its minimum. Once both minions go idle, refresh_minion_pool powers the excess one off, then re-running both transfers concurrently reallocates and powers it back on
before reuse.

Adds coverage for minion pool machine deletion on refresh, mirroring the minion pool power cycle tests but with the default "delete" retention strategy: once the pool's excess machine (beyond its minimum) goes idle, refreshing the pool deletes it instead of powering it off.

Adds coverage for minion pool refresh cron startup recovery: _init_pools_refresh_cron_jobs runs once, when a minion manager service endpoint is constructed, to re-register periodic refresh jobs for any pools that were already ALLOCATED (e.g.: after a service restart).

Adds coverage for the auto-deploy deployer handoff. The integration test test_execution_auto_deploy did have auto_deploy=True, but it never actually waited the deployment to complete. When auto_deploy is True, deployer_manager is supposed to kick off the deployment automatically after the transfer completes.

Adds test_execution_auto_deploy_transfer_failure test, which injects a failure into the deployer's transfer execution and waits for the deployment to be moved to the ERROR state.