[SPARK-22686][SQL] DROP TABLE IF EXISTS should not show AnalysisException

## What changes were proposed in this pull request?

During [SPARK-22488](#19713) to fix view resolution issue, there occurs a regression at `2.2.1` and `master` branch like the following. This PR fixes that.

```scala
scala> spark.version
res2: String = 2.2.1

scala> sql("DROP TABLE IF EXISTS t").show
17/12/04 21:01:06 WARN DropTableCommand: org.apache.spark.sql.AnalysisException:
Table or view not found: t;
org.apache.spark.sql.AnalysisException: Table or view not found: t;
```

## How was this patch tested?

Manual.

Author: Dongjoon Hyun <[email protected]>

Closes #19888 from dongjoon-hyun/SPARK-22686.

Author: dongjoon-hyun

sql/core/src/main/scala/org/apache/spark/sql/execution/command/ddl.scala

@@ -203,14 +203,20 @@ case class DropTableCommand(
         case _ =>
       }
     }
-    try {
-      sparkSession.sharedState.cacheManager.uncacheQuery(sparkSession.table(tableName))
-    } catch {
-      case _: NoSuchTableException if ifExists =>
-      case NonFatal(e) => log.warn(e.toString, e)
+
+    if (catalog.isTemporaryTable(tableName) || catalog.tableExists(tableName)) {
+      try {
+        sparkSession.sharedState.cacheManager.uncacheQuery(sparkSession.table(tableName))
+      } catch {
+        case NonFatal(e) => log.warn(e.toString, e)
+      }
+      catalog.refreshTable(tableName)
+      catalog.dropTable(tableName, ifExists, purge)
+    } else if (ifExists) {
+      // no-op
+    } else {
+      throw new AnalysisException(s"Table or view not found: ${tableName.identifier}")
     }
-    catalog.refreshTable(tableName)
-    catalog.dropTable(tableName, ifExists, purge)
     Seq.empty[Row]
   }
 }