UPPER CASE HOST NAME ANYMORE

Description:
It is not possible to drop users with host names with upper case
letters in them. i.e DROP USER 'root'@'Tmp_Host_Name'; is failing
with error.

Analysis: Since the fix 11748570 we came up with lower case hostnames
as standard. But in the current bug the hostname is created by
mysql_install_db script is still having upper case hostnames. 
So, if we have the hostname with upper case letters like(Tmp_Host_Name)
then we will have as it is stored in the mysql.user table. 
In this case if use "'DROP USER 'root'@'Tmp_Host_Name';" it gives 
error because we do compare with the lower case of hostname since the 
11748570 fix.

Fix: We need to convert the hostname to lower case before storing into 
the mysql.user table when we run the mysql_install_db script.