Update post/multi/gather/env

* Use cmd_exec

Author: jvazquez-r7

modules/post/multi/gather/env.rb

@@ -42,7 +42,7 @@ def get_env_shell
       @ltype = "unix.environment"
       cmd = "env"
     end
-    @output = session.shell_command_token(cmd)
+    @output = cmd_exec(cmd)
   end
 
   def get_env_meterpreter