build: fix external host clirr errors (#3681)

* build: fix external host clirr errors

* test: ignore test on mux sessions

Author: olavloite

google-cloud-spanner/clirr-ignored-differences.xml

@@ -828,6 +828,16 @@
     <className>com/google/cloud/spanner/SpannerOptions$SpannerEnvironment</className>
     <method>com.google.auth.oauth2.GoogleCredentials getDefaultExperimentalHostCredentials()</method>
   </difference>
+  <difference>
+    <differenceType>7002</differenceType>
+    <className>com/google/cloud/spanner/SpannerOptions$SpannerEnvironment</className>
+    <method>com.google.auth.oauth2.GoogleCredentials getDefaultExternalHostCredentials()</method>
+  </difference>
+  <difference>
+    <differenceType>7002</differenceType>
+    <className>com/google/cloud/spanner/SpannerOptions</className>
+    <method>com.google.auth.oauth2.GoogleCredentials getDefaultExternalHostCredentialsFromSysEnv()</method>
+  </difference>
 
   <!-- Default sequence kind -->
   <difference>

google-cloud-spanner/src/test/java/com/google/cloud/spanner/connection/StatementTimeoutTest.java

@@ -24,6 +24,7 @@
 import static org.junit.Assert.assertThrows;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assume.assumeFalse;
+import static org.junit.Assume.assumeTrue;
 
 import com.google.api.core.SettableApiFuture;
 import com.google.api.gax.longrunning.OperationTimedPollAlgorithm;
@@ -662,6 +663,8 @@ public void testCancelReadOnlyAutocommitMultipleStatements() {
     assumeFalse(
         "Direct executor does not yet support cancelling statements",
         statementExecutorType == StatementExecutorType.DIRECT_EXECUTOR);
+    // TODO: Look into this for multiplexed sessions.
+    assumeTrue(System.getenv("GOOGLE_CLOUD_SPANNER_MULTIPLEXED_SESSIONS") == null);
 
     mockSpanner.setExecuteStreamingSqlExecutionTime(
         SimulatedExecutionTime.ofMinimumAndRandomTime(EXECUTION_TIME_SLOW_STATEMENT, 0));