[SPARK-19113][SS][TESTS] Ignore StreamingQueryException thrown from awaitInitialization to avoid breaking tests

## What changes were proposed in this pull request?

apache#16492 missed one race condition: `StreamExecution.awaitInitialization` may throw fatal errors and fail the test. This PR just ignores `StreamingQueryException` thrown from `awaitInitialization` so that we can verify the exception in the `ExpectFailure` action later. It's fine since `StopStream` or `ExpectFailure` will catch `StreamingQueryException` as well.

## How was this patch tested?

Jenkins

Author: Shixiong Zhu <shixiong@databricks.com>

Closes apache#16567 from zsxwing/SPARK-19113-2.

Author: zsxwing

sql/core/src/test/scala/org/apache/spark/sql/streaming/StreamTest.scala

@@ -385,7 +385,12 @@ trait StreamTest extends QueryTest with SharedSQLContext with Timeouts {
                 .streamingQuery
             // Wait until the initialization finishes, because some tests need to use `logicalPlan`
             // after starting the query.
-            currentStream.awaitInitialization(streamingTimeout.toMillis)
+            try {
+              currentStream.awaitInitialization(streamingTimeout.toMillis)
+            } catch {
+              case _: StreamingQueryException =>
+                // Ignore the exception. `StopStream` or `ExpectFailure` will catch it as well.
+            }
 
           case AdvanceManualClock(timeToAdd) =>
             verify(currentStream != null,