tests: bgp_evpn_rt5 test match evpn vni

tests: bgp_evpn_rt5 test match evpn vni

0d5bd461af commit was supposed to check that route-map "match evpn vni"
was working by adding a r3 router that injected prefixes with VNI 102.
A route-map on r1 was filtering r3 prefixes. However, the test was
working even after removing r3. A check was needed without the route-map
to check that r3 prefixes were received before applying the filter.

Test "match evpn vni" route-map filtering applied to r2 input instead.

Fixes: 0d5bd461af ("topotests: bgp_evpn_rt5, add test with match evpn vni command")
Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>