topotest: update the LDP VPLS test

The final test case of this topotest wasn't really testing
anything. Do the following changes to fix this:
* Remove "no link-detect" from the zebra configs so that link down
  failures are detected immediately;
* After shutting down the interface between r1 and r2, wait five
  seconds before testing if the pseudowires reconverged through
  the r3 router.

Signed-off-by: Renato Westphal <renato@opensourcerouting.org>

tests/topotests/ldp-vpls-topo1/r1/zebra.conf

@@ -14,17 +14,14 @@ interface lo
 !
 interface r1-eth0
  description to s1
- no link-detect
 !
 interface r1-eth1
  description to s4
  ip address 10.0.1.1/24
- no link-detect
 !
 interface r1-eth2
  description to s5
  ip address 10.0.2.1/24
- no link-detect
 !
 ip forwarding
 !

tests/topotests/ldp-vpls-topo1/r2/zebra.conf

@@ -13,17 +13,14 @@ interface lo
 !
 interface r2-eth0
  description to s2
- no link-detect
 !
 interface r2-eth1
  description to s4
  ip address 10.0.1.2/24
- no link-detect
 !
 interface r2-eth2
  description to s6
  ip address 10.0.3.2/24
- no link-detect
 !
 ip forwarding
 !

tests/topotests/ldp-vpls-topo1/r3/zebra.conf

@@ -13,17 +13,14 @@ interface lo
 !
 interface r3-eth0
  description to s3
- no link-detect
 !
 interface r3-eth1
  description to s5
  ip address 10.0.2.3/24
- no link-detect
 !
 interface r3-eth2
  description to s6
  ip address 10.0.3.3/24
- no link-detect
 !
 ip forwarding
 !

tests/topotests/ldp-vpls-topo1/test_ldp_vpls_topo1.py

@@ -257,6 +257,7 @@ def test_ldp_pseudowires_after_link_down():
     # Shut down r1-r2 link */
     tgen = get_topogen()
     tgen.gears['r1'].peer_link_enable('r1-eth1', False)
+    topotest.sleep(5, "Waiting for the network to reconverge")
 
     # check if the pseudowire is still up (using an alternate path for nexthop resolution)
     for rname in ['r1', 'r2', 'r3']: