relax fuse_device neverallow rules

The fuse_device neverallow rules are too aggressive and are inhibiting
certain vendor customizations. Relax the /dev/fuse neverallow rules so
that they better reflect the security invariants we want to uphold.

Bug: 37496487
Test: policy compiles.
Change-Id: Ie73b0ba7c76446afc2a7a23ebed1275c977d932d