Fix quicknanobrowser to use unique storage location

Do not use "Default" as custom profile, global profile
uses "Default" as storge name, this ends up
on creating two browser context adapters using the same files.

Change-Id: I298fa87ee14c5c83a15683710ba3fbb29c201714
Reviewed-by: Peter Varga <pvarga@inf.u-szeged.hu>
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>