Set default value for 'mBpfSupported' to fix asan issue in unit test.

Failed test case: BandwidthControllerTest.ManipulateSpecialApps

Bug: 117967202
Test: netd_unit_test, netd_integration_test, AddressSanitizer
Change-Id: Ibf86a6becb5c1dc5cc3d142f4b3cc7276bf40ca9
diff --git a/server/BandwidthController.h b/server/BandwidthController.h
index 0b76134..31575b8 100644
--- a/server/BandwidthController.h
+++ b/server/BandwidthController.h
@@ -131,7 +131,7 @@
     static const char *opToString(IptOp op);
     static const char *jumpToString(IptJumpOp jumpHandling);
 
-    bool mBpfSupported;
+    bool mBpfSupported = false;
 
     int64_t mSharedQuotaBytes = 0;
     int64_t mSharedAlertBytes = 0;