Merge branch 'dev' into agent-master-2

Downgrade execve version to 18 in driver

draios#1044 changed the event number for
execve events from 18 to 19, in order to add the pgid to the exit event.

We want that event to be supported in open source sysdig, and to be
known to the agent, but not generated by the agent yet. So we'll change
the driver event table to use version 18 for execve events instead of
19, and to return only those fields present in execve version 18.

A later PR will undo this change, causing the driver to generate execve
events with version 19. At that time, open source sysdig will be widely
available and users can read the events in captures.

Add more validation of mesos task ids. (draios#1057)

In some cases, the value of MESOS_TASK_ID in the environment might be a
trivial value like "0", "1", etc. In these cases, don't consider the
container to be a valid mesos container at all.

Add filtercheck fd.connected

Add support for the filtercheck fd.connected, that returns true
for connected sockets.

add s390x as platform with warning (draios#1029)

Fix nullptr dereference in init_k8s_ssl()

Merge branch 'dev' into falco-master

Revert "Add process group id to execve events (draios#950) (draios#1035…

…)"

This reverts commit a4a0f32.

Handle null return from sinsp_evt::get_thread_info() (draios#1039)

Revert "Add process group id to execve events (draios#950)"

This reverts commit b4747df.