Add namespace testing for DoAll in tools_net_unittest.cpp

Signed-off-by: Rui Zhang <ruizhan@google.com>
Change-Id: I9490146aee23b93adab47a9604f5567a1d6235eb
diff --git a/tools/test/tools_net_unittest.cpp b/tools/test/tools_net_unittest.cpp
index faf68d0..c5b8419 100644
--- a/tools/test/tools_net_unittest.cpp
+++ b/tools/test/tools_net_unittest.cpp
@@ -18,6 +18,7 @@
 using ::testing::_;
 using ::testing::AllOf;
 using ::testing::ContainerEq;
+using ::testing::DoAll;
 using ::testing::Field;
 using ::testing::Gt;
 using ::testing::InSequence;