Optimize calls to build_table_filenames for CREATE TABLE

• When doing create table, we call build_table_filename 3 times:
• In ha_table_exists() as part of upgrade_lock_if_not_exists()
• Here we could mark in create_info if the table existed or not !
• In mysql_create_table_no_lock()
• In create_table_imp() to check if the table exists (again)

This task is to only call build_table_filename and ha_table_exists() once for CREATE TABLE

Suggested solution is to call build_table_filename() once at start of create table and store
name (and later a flag if table existed) in HA_CREATE_INFO.