Use protobuf string wrapper in utility_test.cc. (#1625)
Use protobuf string wrapper in utility_test.cc. (#1625)

Required for Google import. The Protobuf::TextFormat::PrintToString
method must use a wrapped string.
dnoe/envoy,fengli79/envoy,tdmackey/envoy,envoyproxy/envoy,envoyproxy/envoy-wasm,envoyproxy/envoy-wasm,craffert0/envoy,istio/envoy,envoyproxy/envoy,amalgam8/envoy,lyft/envoy,rlazarus/envoy,lyft/envoy,lyft/envoy,fengli79/envoy,sebrandon1/envoy,jrajahalme/envoy,istio/envoy,fengli79/envoy,envoyproxy/envoy,eklitzke/envoy,tdmackey/envoy,eklitzke/envoy,jrajahalme/envoy,rlazarus/envoy,jrajahalme/envoy,envoyproxy/envoy,lizan/envoy,envoyproxy/envoy-wasm,jrajahalme/envoy,istio/envoy,eklitzke/envoy,jrajahalme/envoy,craffert0/envoy,amalgam8/envoy,amalgam8/envoy,eklitzke/envoy,craffert0/envoy,dnoe/envoy,istio/envoy,istio/envoy,sebrandon1/envoy,envoyproxy/envoy-wasm,envoyproxy/envoy,lizan/envoy,envoyproxy/envoy-wasm,istio/envoy,envoyproxy/envoy,lizan/envoy,tdmackey/envoy,envoyproxy/envoy,envoyproxy/envoy,rlazarus/envoy,envoyproxy/envoy,eklitzke/envoy,lizan/envoy,dnoe/envoy,rlazarus/envoy,dnoe/envoy,envoyproxy/envoy,jrajahalme/envoy,lizan/envoy,fengli79/envoy,lizan/envoy,tdmackey/envoy,dnoe/envoy,envoyproxy/envoy-wasm,envoyproxy/envoy-wasm,sebrandon1/envoy,amalgam8/envoy,sebrandon1/envoy,lyft/envoy,envoyproxy/envoy,craffert0/envoy,lyft/envoy,eklitzke/envoy,sebrandon1/envoy,envoyproxy/envoy,istio/envoy,lyft/envoy