XXX: CI: Disable hanging test on Travis OSX.

Temporary change to avoid frequent hangs on Travis macOS/OSX builds.
Hang does not occur on Quickbuild OSX (Yosemite) build.
Reverting e9061117a5 avoids the hang, but causes
more serious regressions on many more systems.

Note that the job_spec hang only happens with the gcc-4.9 Travis OSX build.

References #5002
References #5029

test/functional/api/server_requests_spec.lua

@@ -137,6 +137,12 @@ describe('server -> client', function()
   end)
 
   describe('when the client is a recursive vim instance', function()
+    if os.getenv("TRAVIS") and helpers.os_name() == "osx" then
+      -- XXX: Hangs Travis OSX since e9061117a5b8f195c3f26a5cb94e18ddd7752d86.
+      pending("[Hangs on Travis OSX. #5002]", function() end)
+      return
+    end
+
     before_each(function()
       nvim('command', "let vim = rpcstart('"..nvim_prog.."', ['-u', 'NONE', '-i', 'NONE', '--cmd', 'set noswapfile', '--embed'])")
       neq(0, eval('vim'))