merge revision(s) 39179,39245: [Backport #7826]

	the process maybe already finished
	* test/ruby/test_process.rb (test_setsid): Added a workaround for
	  MacOS X. Patch by nagachika. [Bug #7826] [ruby-core:52126]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@39513 b2dd03c8-39d4-4d8f-98ff-823fe69b080e