MDEV-4786 - merge 10.0-monty - 10.0

Fixed main.innodb_mysql_sync failure.

TDC_RT_REMOVE_NOT_OWN_KEEP_SHARE is not same as
TDC_RT_REMOVE_NOT_OWN_AND_MARK_NOT_USABLE. Comment in sql_table.cc says:

      Storage engine has requested exclusive lock only for prepare phase
      and we are not under LOCK TABLES.
      Don't mark TABLE_SHARE as old in this case, as this won't allow opening
      of table by other threads during main phase of in-place ALTER TABLE.

At this moment we hold exclusive metadata lock, all we should do
is purge unused TABLE objects.

sql/sql_base.cc:
  Restore 5.6 behavior of TDC_RT_REMOVE_NOT_OWN_KEEP_SHARE.
sql/sql_base.h:
  Restore 5.6 behavior of TDC_RT_REMOVE_NOT_OWN_KEEP_SHARE.

sql/sql_base.cc

@@ -9611,7 +9611,7 @@ void tdc_remove_table(THD *thd, enum_tdc_remove_table_type remove_type,
       */
       if (remove_type == TDC_RT_REMOVE_NOT_OWN)
         share->remove_from_cache_at_close();
-      else
+      else if (remove_type != TDC_RT_REMOVE_NOT_OWN_KEEP_SHARE)
       {
         /* Ensure that no can open the table while it's used */
         share->protect_against_usage();

sql/sql_base.h

@@ -61,8 +61,8 @@ enum find_item_error_report_type {REPORT_ALL_ERRORS, REPORT_EXCEPT_NOT_FOUND,
 
 enum enum_tdc_remove_table_type {TDC_RT_REMOVE_ALL, TDC_RT_REMOVE_NOT_OWN,
                                  TDC_RT_REMOVE_UNUSED,
-                                 TDC_RT_REMOVE_NOT_OWN_AND_MARK_NOT_USABLE};
-#define TDC_RT_REMOVE_NOT_OWN_KEEP_SHARE TDC_RT_REMOVE_NOT_OWN_AND_MARK_NOT_USABLE
+                                 TDC_RT_REMOVE_NOT_OWN_AND_MARK_NOT_USABLE,
+                                 TDC_RT_REMOVE_NOT_OWN_KEEP_SHARE};
 
 /* bits for last argument to remove_table_from_cache() */
 #define RTFC_NO_FLAG                0x0000