Chown doesn't work on mounted vfat.

As reported by a user. Resolves bug 1092560.

Change-Id: I44c847d5e7f3242ca46a7436bcbc6e519baa88fc
Centralize instance directory logic.

This is the first step to being able to change the name of the instance
directories to something more unique than instance name.

Sneaks up on bug 1023865.

Change-Id: I1340a6b8644680325cba1e90a208e4be33ace6b4
Merge "Chown doesn't work on mounted vfat."
Merge "Centralize instance directory logic."