NETOBSERV-1198: drop_cause enum in vmlinux are based off old kernel (#161)

* allow tracing more drops and avoid early return

sometimes we can don't have socket struct valid
which we use to populate TCP state in that case
we keep state as 0 and we proceed generating drop
flow

Signed-off-by: msherif1234 <mmahmoud@redhat.com>

* NETOBSERV-1198: drop_cause enum in vmlinux

Signed-off-by: msherif1234 <mmahmoud@redhat.com>

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Signed-off-by: msherif1234 <mmahmoud@redhat.com>