ha_innobase::delete_table(): When the table that is being dropped
has a name starting with #sql, temporarily set
innodb_lock_wait_timeout=0 while attempting to lock the
persistent statistics tables. If the statistics tables cannot be locked,
pretend that statistics did not exist and carry on with dropping
the table. The SQL layer is not really prepared for failures of
this operation. This is what fixes the test case.

ha_innobase::rename_table(): When renaming a table from a name
that starts with #sql, try to lock the statistics tables with an
immediate timeout, and ignore the statistics if the locks were
not available. In fact, during any rename from a #sql name,
dict_stats_rename_table() should have no effect, because already
when an earlier rename to a #sql name took place we should have
deleted the statistics for the table using the non-#sql name.
This change is just analogous to the ha_innobase::delete_table().