Merge pull request hashicorp#1714 from aszeszo/master

Use proper detection for Solaris

plugins/guests/solaris/guest.rb

@@ -7,7 +7,7 @@ module GuestSolaris
     # Contributed by Blake Irvin <[email protected]>
     class Guest < Vagrant.plugin("2", :guest)
       def detect?(machine)
-        machine.communicate.test("uname -o | grep Solaris")
+        machine.communicate.test("uname -s | grep SunOS")
       end
     end
   end