Fix duplicate symbols error in external/android-clat

Symbol Global_Clatd_Config is duplicated when switch -fcommon to -fno-common

Bug: b/151457797
Test: mm
Change-Id: Ic6beb25cbc370d5bb085a3c569e66bae87446a49
diff --git a/clatd_test.cpp b/clatd_test.cpp
index 94ae0b5..0ed5f28 100644
--- a/clatd_test.cpp
+++ b/clatd_test.cpp
@@ -559,8 +559,6 @@
   }
 }
 
-struct clat_config Global_Clatd_Config;
-
 class ClatdTest : public ::testing::Test {
  protected:
   static TunInterface sTun;