Avoid clearing default browser setting when unnecessary

If the priority parameter of a browser app's intent-filter in Manifest
is less than 0, it can not be selected by user. So it shoult not clear
default browser settings.

Bug: Install more than one browser apps, and pick one as default,
then install com.taobao.taobao. Default settings will be cleared.
Test: N/A

Change-Id: Ib24d80a025ae848cb90ada436cf65bf8cbed785f
Signed-off-by: tiansiming <tiansiming@xiaomi.com>