Fix evaluation of SQLite driver options

Ensure that the options, which are passed to the SQLite driver, are
evaluated in the correct order and do not overwrite each other.
According to http://www.sqlite.org/c3ref/open.html

 the
SQLITE_OPEN_READONLY and (SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE) are
mutual exclusive, but SQLITE_OPEN_URI can be combined with both of them.

Task-number: QTBUG-35186
[ChangeLog][QtSql][QSQLITE] Fixed evaluation of driver options
Change-Id: I8e74fe1ce43b9118b15f7b13fc71670bdcd73f68
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
Reviewed-by: Mark Brand <mabrand@mabrand.nl>