LP:695304 - Incorrect value reported for optimizer_switch by maria-5.3-wl21

When constructing and reporting the current value of optimizer_switch , maria-5.3-wl21 does not put a comma between index_merge_sort_union and index_condition_pushdown. This prevents the value from being parsed properly

To repeat:

sql/mysqld --verbose --help | grep optimizer_switch

optimizer_switch index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=offindex_condition_pushdown=on,firstmatch=on,loosescan=on,materialization=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,table_elimination=on

Note the string contains "index_merge_sort_intersection=offindex_condition_pushdown=on" with no comma.

If the variable is accessed via SELECT @@optimizer_switch or via information_schema, the correct value is reported