[#21756] YSQL: Stabilize testYbTerminatedQueriesMultipleCauses with Connection Manager enabled

Summary:
When connection manager is enabled, the test org.yb.pgsql.TestPgYbStat.testYbTerminatedQueriesMultipleCauses fails.

During the runtime of the test, the backend process is explicitly killed, and the test expects a corresponding error message. With the introduction of the connection manager layer, the error message is instead sent by odyssey, which causes the assertion to fail.

By expecting a different error message when connection manager is used as an endpoint, this test passes.

Jira: DB-10630

Test Plan:
Jenkins: enable connection manager, test regex: .*TestPgYbStat.*

./yb_build.sh --enable-ysql-conn-mgr-test --java-test org.yb.pgsql.TestPgYbStat#testYbTerminatedQueriesMultipleCauses

Reviewers: janand, telgersma

Reviewed By: janand, telgersma

Differential Revision: https://phorge.dev.yugabyte.com/D33464

Author: rahulb-yb

java/yb-pgsql/src/test/java/org/yb/pgsql/TestPgYbStat.java

@@ -72,7 +72,10 @@ private void executeQueryAndSendSignal(final String query,
         try {
           statement.execute(query);
         } catch (Throwable throwable) {
-          assertEquals("An I/O error occurred while sending to the backend.",
+          if(isTestRunningWithConnectionManager())
+            assertTrue(throwable.getMessage().contains("remote server read/write error"));
+          else
+            assertEquals("An I/O error occurred while sending to the backend.",
                        throwable.getMessage());
         }
       });