bpf: Allow also for 0 seconds graceful shutdown timeout
bpf: Allow also for 0 seconds graceful shutdown timeout

Given this is in seconds, a 0 sec timeout for TCP won't otherwise trigger
if selected by the user.

Reported-by: Martynas Pumputis <6b0d31c0d563223024da45691584643ac78c96e8@lambda.lt>
Signed-off-by: Daniel Borkmann <3d0f3b9ddcacec30c4008c5e030e6c13a478cb4f@iogearbox.net>

michi-covalent/cilium,cilium/cilium,cilium/cilium,michi-covalent/cilium,michi-covalent/cilium,michi-covalent/cilium,cilium/cilium,cilium/cilium,cilium/cilium,michi-covalent/cilium