kas-container: podman: Remove --pid=host

We were using the host PID namespace as workaround for problems related
to binfmt and its missing namespace support. As it turns out after
running a bunch of tests this is no longer necessary.

This patch "reverts" 6b025e4910b4 ("kas-docker: Podman: Fixing isar builds
failing with exec format errors").

Test matrix:

kas layer               podman 3.4.4        podman 3.0.1       podman 3.4.4
                        on Fedora 35        on Debian 11       on Debian 11
                                                          (podman from testing)
xenomai-images
 ISAR_CROSS_COMPILE = 1     OK                 OK                 OK
 ISAR_CROSS_COMPILE = 0     OK                 OK                 OK

iot-2000                    OK                 FAIL [1]           FAIL [1]

[1] The iot-2000 layer is not ISAR based, so we do not run in privileged
mode for such builds which seems to make a difference when using the
--userns=keep-id argument. As it works on Fedora and the error message
indicates "creating of systemd unit failed" it might by systemd related.

podman run --rm -t -i --userns=keep-id debian:buster-slim
Fedora: OK
Debian: Fail
  Error: OCI runtime error: error creating systemd unit
  `libpod-<snip>.scope`: got `failed`

Signed-off-by: Florian Bezdeka <florian.bezdeka@siemens.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

kas-container

@@ -84,7 +84,6 @@ enable_isar_mode() {
 	if [ "${KAS_CONTAINER_ENGINE}" = "podman" ]; then
 		# sudo is needed for a privileged podman container
 		KAS_CONTAINER_COMMAND="sudo ${KAS_CONTAINER_COMMAND}"
-		KAS_ISAR_ARGS="${KAS_ISAR_ARGS} --pid=host"
 	fi
 }