tests: Add topotest for OSPF multi-instance default origination.

This change adds a topotest to test various case of OSPF multi-instance
origination including cases where the criteria route is from another
instance of OSPF, as well as the same OSPF instance (where a default
should not be originated).

Signed-off-by: Acee Lindem <acee@lindem.com>

tests/topotests/ospf_multi_instance/r1/frr.conf

@@ -0,0 +1,19 @@
+!
+hostname r1
+password zebra
+log file /tmp/r1-frr.log
+ip forwarding
+!
+interface lo
+ ip address 1.1.1.1/32
+ ip ospf area 0
+!
+interface r1-eth0
+ ip address 10.1.1.1/24
+ ip ospf area 0
+!
+!
+router ospf
+  ospf router-id 1.1.1.1
+  distance 20
+!

tests/topotests/ospf_multi_instance/r2/frr.conf

@@ -0,0 +1,37 @@
+!
+hostname r2
+password zebra
+! debug ospf event
+! debug ospf lsa
+! debug ospf default-information
+! debug ospf zebra redistribute
+
+ip forwarding
+!
+interface lo1
+ ip address 2.2.2.1/32
+ ip ospf 1 area 0
+ no shut
+!
+interface lo2
+ ip address 2.2.2.2/32
+ ip ospf 2 area 0
+ no shut
+!
+interface r2-eth0
+ ip address 10.1.1.2/24
+ ip ospf 1 area 0
+!
+interface r2-eth1
+ ip address 10.1.2.2/24
+ ip ospf 2 area 0
+!
+router ospf 1
+  ospf router-id 2.2.2.1
+  distance 20
+!
+router ospf 2
+  ospf router-id 2.2.2.2
+  distance 20
+!
+

tests/topotests/ospf_multi_instance/r3/frr.conf

@@ -0,0 +1,19 @@
+!
+hostname r3
+password zebra
+log file /tmp/r3-frr.log
+ip forwarding
+!
+interface lo
+ ip address 3.3.3.1/32
+ ip ospf area 0
+!
+interface r3-eth0
+ ip address 10.1.2.3/24
+ ip ospf area 0
+!
+!
+router ospf
+  ospf router-id 3.3.3.1
+  distance 20
+!