ipv4: add 'dhcp4_outages_in_various_situation' test
This test merges various tests together to save time
- renewal_gw_after_dhcp_outage_for_assumed_var1
- renewal_gw_after_dhcp_outage_for_assumed_var0
- renewal_gw_after_long_dhcp_outage
- renewal_gw_after_dhcp_outage
Those old tests shouldn't be running since 1.11+
@Build:master