Fix another string-compare warning

packages/modules/DnsResolver/tests/resolv_integration_test.cpp:4695:25: error: result of comparison against a string literal is unspecified (use an explicit string comparison function instead) [-Werror,-Wstring-compare]
            if (dnsMode == "STRICT") parcel.tlsName = kDefaultPrivateDnsHostName;
                        ^  ~~~~~~~~
packages/modules/DnsResolver/tests/resolv_integration_test.cpp:4708:29: error: result of comparison against a string literal is unspecified (use an explicit string comparison function instead) [-Werror,-Wstring-compare]
                    dnsMode == "STRICT" ? expectAnswersNotValid(fd, -ETIMEDOUT)
                            ^  ~~~~~~~~
packages/modules/DnsResolver/tests/resolv_integration_test.cpp:4725:25: error: result of comparison against a string literal is unspecified (use an explicit string comparison function instead) [-Werror,-Wstring-compare]
            if (dnsMode == "STRICT" && config.asyncHandshake &&
                        ^  ~~~~~~~~
packages/modules/DnsResolver/tests/resolv_integration_test.cpp:4769:25: error: result of comparison against a string literal is unspecified (use an explicit string comparison function instead) [-Werror,-Wstring-compare]
            if (dnsMode == "STRICT") parcel.tlsName = kDefaultPrivateDnsHostName;
                        ^  ~~~~~~~~
packages/modules/DnsResolver/tests/resolv_integration_test.cpp:4784:25: error: result of comparison against a string literal is unspecified (use an explicit string comparison function instead) [-Werror,-Wstring-compare]
            if (dnsMode == "STRICT" && queryTimeoutMs != INFINITE_QUERY_TIMEOUT) {
                        ^  ~~~~~~~~

Test: presubmit
Bug: 153764102
Change-Id: I7de355469c5fb18261194af346e8760369342b44