lineage: modernize functions

[installrecovery]
 * Don't try to mount system

[installboot]
 * Kill kernel module pushing
 * Now we don't need to mount system anymore ^.^

[eat]
 * No need to use /cache/recovery/command when we have
   adb reboot sideload-auto-reboot
 * Make use of our custom adb wait-for-online

[_adb_connected]
 * Could be removed entirely, but for now make it use
   adb wait-for-online

Change-Id: Ife25e63c63c784670c7d330f8a69de01326de1a0