Keep 'show log' on screen until user dismisses it

Also increase log output to 24 lines

Change-Id: I11381e347c2238f2058ea97f9143476ec3a80cf6
dedupe: backup & restore selinux contexts.

- patch set 2: remove the comment line, adjust freecon.

Change-Id: Ib691146f5e4d33014aac2b540aefc06657818eb4
Merge branch 'cm-11.0' of https://github.com/CyanogenMod/android_bootable_recovery into cm-11.0