vold: Support for moving crypto metadata

 * We have a situation where we need to move the crypto metadata
   from a partition footer to a new place. Add support for this.

Change-Id: I5ccc312f7f062d8a8215530957da9c6283ed7ca5
Merge branch 'cm-11.0' of https://github.com/CyanogenMod/android_system_vold into temp