Mix: Don't start esshd application if we don't need it.

mix.exs

@@ -40,9 +40,16 @@ def project do
   #
   # Type `mix help compile.app` for more information.
   def application do
+    extra_applications = [:logger, :runtime_tools, :comeonin, :quack]
+    extra_applications = if Application.get_env(:esshd, :enabled, false) do
+      [:esshd | extra_applications]
+    else
+      extra_applications
+    end
+
     [
       mod: {Pleroma.Application, []},
-      extra_applications: [:logger, :runtime_tools, :comeonin, :esshd, :quack],
+      extra_applications: extra_applications,
       included_applications: [:ex_syslogger]
     ]
   end