Merge branch 'develop' of github.com:emqx/emqx into develop

rebar.config

@@ -5,7 +5,7 @@
      {cowboy, "2.7.0"},
      {gproc, "0.8.0"},
      {esockd, {git, "https://github.com/emqx/esockd", {tag, "5.6.0"}}},
-     {ekka, {git, "https://github.com/emqx/ekka", {tag, "0.7.0"}}},
+     {ekka, {git, "https://github.com/emqx/ekka", {tag, "0.7.1"}}},
      {gen_rpc, {git, "https://github.com/emqx/gen_rpc", {tag, "2.4.1"}}},
      {cuttlefish, {git, "https://github.com/emqx/cuttlefish", {tag, "v3.0.0"}}}
     ]}.