Fix pid_uid

lib/msf/core/post/linux/system.rb

@@ -218,12 +218,9 @@ module System
   # @return [String]
   #
   def pid_uid(pid)
-    file_pid = "/proc/" + pid.to_s + "/status"
-    result = read_file(file_pid)
-    return result
+    read_file("/proc/#{pid}/status").to_s
   end
 
-
   #
   # Checks if `file_path` is mounted on a noexec mount point
   # @return [Boolean]