test_dhcp_vrf and test_dhcpv6_vrf resolved the DHCP client's PID, then read the VRF's process list and asserted the PID appeared in it. The client re-executes itself at moments of its own choosing, so between those two steps it can come back with a new PID - the process is in the VRF, it simply is not the process we asked about:

AssertionError: '13502' not found in '14322  dhclient\n14324  dhclient-script\n14485  dhclient...'

Observed failing and passing on the same image, so it costs a rerun rather than telling anyone anything.