Update nmap

* Use cmd_exec

Author: jvazquez-r7

modules/exploits/freebsd/local/mmap.rb

@@ -55,7 +55,7 @@ def initialize(info={})
   end
 
   def check
-    res = session.shell_command_token("uname -a")
+    res = cmd_exec('uname -a')
     return Exploit::CheckCode::Appears if res =~ /FreeBSD 9\.[01]/
 
     Exploit::CheckCode::Safe