Fix memory leak in NetBpfLoad

The lambda was capturing btf by value instead of reference. This meant
that btf__free was never called, because at the time of capture btf was
null.

This changes the lambda to capture btf by reference instead of by value.

Test: TH
Flag: EXEMPT mainline
Bug: 411323352
Change-Id: I6c6637b10f16d48f9ae5b702e44883046b46e252
1 file changed