Reason:
 This is a regression happened because of changes done in code refactoring 
 in 5.1 from 5.0.

Issue: 
 While doing "Show tables" lex->verbose was being checked to avoid opening
 FRM files to get table type. In case of "Show full table", lex->verbose
 is true to indicate table type is required. In 5.0, this check was
 present which got missing in >=5.5.

Fix:
 Added the required check to avoid opening FRM files unnecessarily in case
 of "Show tables".