recovery: default recovery updating to false

Default recovery flashing on system updates to false. This can be
overridden for specific builds/devices, but the option can be enabled
or disabled on all builds.

Change-Id: Ia1bc94bd1e5f799fc894286a6b2f4f7a8a3816dd
Merge pull request #25 from CyanogenMod/cm-11.0

recovery: default recovery updating to false