Upgrade emqtt and emqx-ct-helper deps

- Upgrade emqtt to v1.2.0
- Upgrade emqx-ct-helpers to v1.2.2

rebar.config

@@ -39,8 +39,8 @@
  [{test,
    [{deps,
      [{bbmustache, "1.7.0"},
-      {emqtt, {git, "https://github.com/emqx/emqtt", {branch, "develop"}}},
-      {emqx_ct_helpers, {git, "https://github.com/emqx/emqx-ct-helpers", {branch, "develop"}}}
+      {emqtt, {git, "https://github.com/emqx/emqtt", {tag, "1.2.0"}}},
+      {emqx_ct_helpers, {git, "https://github.com/emqx/emqx-ct-helpers", {tag, "1.2.2"}}}
      ]},
     {erl_opts, [debug_info]}
    ]}