backtrace: Break when reaching ip of 0
backtrace: Break when reaching ip of 0

All backtraces end with ip of 0 for some reason, which will be printed
as 0xffffffffffffffff (we print ip - 1). Drop it to reduce noise.

scylladb/seastar,cloudius-systems/seastar,avikivity/seastar,avikivity/seastar,dreamsxin/seastar,cloudius-systems/seastar,syuu1228/seastar,syuu1228/seastar,dreamsxin/seastar,syuu1228/seastar,scylladb/seastar,dreamsxin/seastar,avikivity/seastar,cloudius-systems/seastar,scylladb/seastar