Revert "vold: support more than 1 UMS share"

This reverts commit 2209cf1ad2a147abe7b6e64d2380416ed26cdc2f.
Revert "vold: don't crash when formatting unformatted volume"

This reverts commit 60b9e2ff0a254433718ff830342ed9a7d31950b6.
Revert "vold: add ro.vold.umsdirtyratio property"

This reverts commit ff7a04d6ebc22f3b5c89d495d225650648c5b862.