User grants debug Mysql part: first steps

Select all user/host instead of just user
so we'll have 'root'@'localhost', 'root'@'127.0.0.1', etc. instead of just root

Next step: retrieve IS_GRANTABLE value (so patch mysqlcppconn)

Change-Id: Ib0ce7d0745ace17ce8058f3ff9806bea2bdc56f1
Reviewed-on: https://gerrit.libreoffice.org/7140
Reviewed-by: Lionel Elie Mamane <lionel@mamane.lu>
Tested-by: Lionel Elie Mamane <lionel@mamane.lu>