HBASE-20258 Shell hangs when scanning a disabled table

Signed-off-by: Mike Drob <mdrob@apache.org>

hbase-shell/src/main/ruby/shell/commands.rb

@@ -116,6 +116,9 @@ module Shell
           raise "Unknown table #{strs[0]}!" if strs.size == 1
           raise "Unknown table #{args.first}!"
         end
+        if cause.is_a?(org.apache.hadoop.hbase.TableNotEnabledException)
+          raise "Table #{args.first} is disabled!"
+        end
         if cause.is_a?(org.apache.hadoop.hbase.UnknownRegionException)
           raise "Unknown region #{args.first}!"
         end

hbase-shell/src/test/ruby/hbase/table_test.rb

@@ -695,5 +695,16 @@ module Hbase
       assert_equal(0, splits.size)
       assert_equal([], splits)
     end
+
+    define_test "scan should throw an exception on a disabled table" do
+      @test_table.disable
+      begin
+        assert_raise(RuntimeError) do
+          @test_table.scan
+        end
+      ensure
+        @test_table.enable
+      end
+    end
   end
 end