Get FAT volume ID through vold.

Now that storage volumes are FUSE-wrapped, userspace apps no longer
have access to perform the direct ioctl().

Bug: 11175082
Change-Id: I08b8367a89e4f325dd28c29789165e95c70e9944
Avoid NPE when checking for empty volume.

Bug: 11175082
Change-Id: Ie35da00babeabaaf39d3afb2da53b39e80bddaac
Also check legacy path

b/9604671

Change-Id: I49035ed53dab71cdacb7f3cdd59c18e8bb5ba850
Check granted permissions for all paths

b/9604671
b/10345049
b/11380658

Change-Id: Ifa4db10261f39e5af5fe84902f7221075a78bad3
Fix argument references

The bucket id and display names references were off by one, resulting
in brokenness when renaming a directory via MTP
b/10835798
b/11655617

Change-Id: I9e6c510027a37deed55887393e388805f06b86b0