init: various changes

*) do not use flash storages to generate entropy
*) set io scheduler to noop on bootup and to row on boot complete
*) disable blinking buttons at service.bootanim.exit
*) use sys.boot_completed instead of dev.bootcomplete

Change-Id: I508f74ef98ec071081c50a4658d5cd183f805060
fstab: new mount flags

Change-Id: I5750dbce745f749cea85759f85f8d5de7d4756ac