ANDROID: fuse-bpf: Simplify and fix setting bpf program

Fix case when an existing bpf prog is being removed
Tidy up code

Bug: 279363668
Test: Boots, can copy file to /sdcardfs/Android/data, fuse_test passes
Signed-off-by: Paul Lawrence <paullawrence@google.com>
(cherry picked from https://android-review.googlesource.com/q/commit:64366661e8a9a6d691e5ab6499872d495aed5266)
Merged-In: If0e682f43cbeb62764a7a2be543b90cb974b0aa0
Change-Id: If0e682f43cbeb62764a7a2be543b90cb974b0aa0