More s/us fixes

db/column_family_test.cc

@@ -347,7 +347,7 @@ TEST(ColumnFamilyTest, DontReuseColumnFamilyID) {
     CreateColumnFamilies({"three2"});
     // ID 3 that was used for dropped column family "three" should not be reused
     auto cfh3 = reinterpret_cast<ColumnFamilyHandleImpl*>(handles_[3]);
-    ASSERT_EQ(4, cfh3->GetID());
+    ASSERT_EQ(4U, cfh3->GetID());
     Close();
     Destroy();
   }

utilities/backupable/backupable_db_test.cc

@@ -179,7 +179,7 @@ class TestEnv : public EnvWrapper {
   }
 
   virtual Status DeleteFile(const std::string& fname) override {
-    ASSERT_GT(limit_delete_files_, 0);
+    ASSERT_GT(limit_delete_files_, 0U);
     limit_delete_files_--;
     return EnvWrapper::DeleteFile(fname);
   }