'SYSTEM LOCK' IN PROCESSLIST

Analysis
=========
Show processlist shows 'System Lock' in 'State' field while
LOAD DATA INFILE is running.

thd->proc_info update is missing in LOAD DATA INFILE path.
Thus any request will get last unpdated status from lock_table()
during open_table().

Fix:
=======
Update state information from LOAD DATA INFILE path.