Fix failure in SearchCancellationIT.testMSearchChildReqCancellationWi…

…thHybridTimeout (opensearch-project#1105)

In some cases as one shared with issue opensearch-project#1099, the maxConcurrentSearchRequests was chosen as 0 which
will compute the final value during execution of the request based on processor counts. When this
computed value is less than number of search request in msearch request, it will execute all the
requests in multiple iterations causing the failure since test will only wait for one such
iteration. Hence setting the maxConcurrentSearchRequests explicitly to number of search requests
being added in the test to ensure correct behavior

Signed-off-by: Sorabh Hamirwasia <sohami.apache@gmail.com>

server/src/internalClusterTest/java/org/opensearch/search/SearchCancellationIT.java

@@ -509,7 +509,7 @@ public void testMSearchChildRequestCancellationWithClusterLevelTimeout() throws
         client().admin().cluster().prepareUpdateSettings().setPersistentSettings(Settings.builder()
             .put(SEARCH_CANCEL_AFTER_TIME_INTERVAL_SETTING_KEY, cancellationTimeout)
             .build()).get();
-        ActionFuture<MultiSearchResponse> mSearchResponse = client().prepareMultiSearch()
+        ActionFuture<MultiSearchResponse> mSearchResponse = client().prepareMultiSearch().setMaxConcurrentSearchRequests(2)
             .add(client().prepareSearch("test").setAllowPartialSearchResults(randomBoolean())
                 .setQuery(scriptQuery(new Script(ScriptType.INLINE, "mockscript", ScriptedBlockPlugin.SCRIPT_NAME,
                     Collections.emptyMap()))))
@@ -541,7 +541,7 @@ public void testMSearchChildReqCancellationWithHybridTimeout() throws Exception
         client().admin().cluster().prepareUpdateSettings().setPersistentSettings(Settings.builder()
             .put(SEARCH_CANCEL_AFTER_TIME_INTERVAL_SETTING_KEY, clusterCancellationTimeout)
             .build()).get();
-        ActionFuture<MultiSearchResponse> mSearchResponse = client().prepareMultiSearch()
+        ActionFuture<MultiSearchResponse> mSearchResponse = client().prepareMultiSearch().setMaxConcurrentSearchRequests(3)
             .add(client().prepareSearch("test").setAllowPartialSearchResults(randomBoolean())
                 .setCancelAfterTimeInterval(reqCancellationTimeout)
                 .setQuery(scriptQuery(new Script(ScriptType.INLINE, "mockscript", ScriptedBlockPlugin.SCRIPT_NAME,