ANDROID: fuse-bpf: Add partial flock support

This adds passthrough support for flock on fuse-bpf files. It does not
give any control via a bpf filter. The flock will act as though it was
taken on the lower file.

Bug: 289882899
Bug: 296641006
Test: fuse_test -t32 (flock_test)
Change-Id: Iba0b9630766cedbd3195532c5e929891593cfe30
Signed-off-by: Daniel Rosenberg <drosen@google.com>
(cherry picked from commit 3c49a491)