selftests: Replace sleep with slowwait

Replace the sleep in kill_procs with slowwait.

Signed-off-by: David Ahern <[e-mail]>
Reviewed-by: Simon Horman <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

tools/testing/selftests/net/fcnal-test.sh

···
 kill_procs()
 {
 	killall nettest ping ping6 >/dev/null 2>&1
-	sleep 1
+	slowwait 2 sh -c 'test -z "$(pgrep '"'^(nettest|ping|ping6)$'"')"'
 }
 
 set_ping_group()