selftests/net: convert fib-onlink-tests.sh to run it in unique namespace

Remove PEER_CMD, which is not used in this test

Here is the test result after conversion.

]# ./fib-onlink-tests.sh
Error: ipv4: FIB table does not exist.
Flush terminated
Error: ipv6: FIB table does not exist.
Flush terminated

########################################
Configuring interfaces

...

TEST: Gateway resolves to wrong nexthop device - VRF [ OK ]

Tests passed: 38
Tests failed: 0

Acked-by: David Ahern <[e-mail]>
Signed-off-by: Hangbin Liu <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

tools/testing/selftests/net/fib-onlink-tests.sh

···
 
 # IPv4 and IPv6 onlink tests
 
+source lib.sh
 PAUSE_ON_FAIL=${PAUSE_ON_FAIL:=no}
 VERBOSE=0
 
···
 # mcast address
 MCAST6=ff02::1
 
-
-PEER_NS=bart
-PEER_CMD="ip netns exec ${PEER_NS}"
 VRF=lisa
 VRF_TABLE=1101
 PBR_TABLE=101
···
 	set -e
 
 	# create namespace
-	ip netns add ${PEER_NS}
-	ip -netns ${PEER_NS} li set lo up
+	setup_ns PEER_NS
 
 	# add vrf table
 	ip li add ${VRF} type vrf table ${VRF_TABLE}
···
 cleanup()
 {
 	# make sure we start from a clean slate
-	ip netns del ${PEER_NS} 2>/dev/null
+	cleanup_ns ${PEER_NS} 2>/dev/null
 	for n in 1 3 5 7; do
 		ip link del ${NETIFS[p${n}]} 2>/dev/null
 	done