podman rm: handle case where conmon was killed

When conmon was killed podman rm -f currently fails but running it again
then works which doesn't really makes sense. We should properly remove
the contianer even if conmon is dead.

In fact the code already handles ErrConmonDead as stop error when we
remove the container but this error was never thrown anywhere. To fix
this throw ErrConmonDead instead of ErrInternal because that is not an
intenral error if something else killed conmon.

With this we can correctly cleanup and remove the container. The fact
that this works on the first try is important for quadlet units as they
only run the ExecStopPost= command once to remove it.

Fixes: #26640

Signed-off-by: Paul Holzinger <pholzing@redhat.com>

libpod/container_internal.go

@@ -1544,7 +1544,7 @@ func (c *Container) waitForConmonToExitAndSave() error {
 				logrus.Errorf("Error cleaning up container %s after Conmon exited prematurely: %v", c.ID(), err)
 			}
 
-			return fmt.Errorf("container %s conmon exited prematurely, exit code could not be retrieved: %w", c.ID(), define.ErrInternal)
+			return fmt.Errorf("container %s conmon exited prematurely, exit code could not be retrieved: %w", c.ID(), define.ErrConmonDead)
 		}
 
 		return c.save()