HBASE-24118 [Flakey Tests] TestCloseRegionWhileRSCrash

Reapply but as an @Ignore for the flakey test.

hbase-server/src/test/java/org/apache/hadoop/hbase/master/assignment/TestCloseRegionWhileRSCrash.java

@@ -160,7 +160,7 @@ public class TestCloseRegionWhileRSCrash {
     UTIL.shutdownMiniCluster();
   }
 
-  @Test
+  @org.junit.Ignore @Test // Until root-cause of flakeyness, HBASE-24117, is addressed.
   public void testRetryBackoff() throws IOException, InterruptedException {
     HRegionServer srcRs = UTIL.getRSForFirstRegionInTable(TABLE_NAME);
     RegionInfo region = srcRs.getRegions(TABLE_NAME).get(0).getRegionInfo();