test: speed up applier reconnect test

The test assumes the `<vardir>/<alias>.sock` URI for a server created by
`luatest.replica_set`. It was correct before [1], but luatest changed
the URI to `<vardir>/<rs>/<alias>.sock`. Commit 0e7e76e ("test:
update tests according to luatest changes") was supposed to adjust the
URIs, but this particular one was missed.

As a result, the test waits 30 seconds for a non-existent peer, but then
succeeds. Here we eliminate this waiting, so the test passes in ~2
seconds.

[1]: tarantool/luatest#300

NO_DOC=test adjustment
NO_CHANGELOG=same

Author: Totktonada

test/replication-luatest/gh_4669_applier_reconnect_test.lua

@@ -1,6 +1,5 @@
 local t = require('luatest')
 local cluster = require('luatest.replica_set')
-local server = require('luatest.server')
 
 local g = t.group('gh-4669-applier-reconnect')
 
@@ -34,9 +33,9 @@ g.test_applier_connection_on_reconfig = function(g)
             replication = {
                 box.cfg.listen,
                 box.cfg.replication[1],
-                "%s/replica2.sock",
+                "%s",
             }
-        }]]):format(server.vardir))
+        }]]):format(g.replica2.net_box_uri))
     g.replica:eval([[
         box.cfg{
             replication = {