This is mere code clean-up; the reported problem was already fixed
in commit 3fdd390791.
row_sel(): Remove the variable search_latch_locked.
row_sel_try_search_shortcut(): Remove the parameter
search_latch_locked, which was always passed as nonzero.
row_sel_try_search_shortcut(), row_sel_try_search_shortcut_for_mysql():
Do not expect the caller to acquire the AHI latch. Instead,
acquire and release it inside this function.
row_search_mvcc(): Remove a bogus condition on mysql_n_tables_locked.
When the btr_search_latch was split into an array of latches
in MySQL 5.7.8 as part of the Oracle Bug#20985298 fix, the "caching"
of the latch across storage engine API calls was removed, and
thus it is unnecessary to avoid adaptive hash index searches
during INSERT...SELECT.
12f804acfa