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
(cherry picked from commit da4c5ecfd0cfce4e784a32784731282221a6af34)
Merge pull request #5 from CyanogenMod/stable/cm-11.0

vold: Support for moving crypto metadata