Fix finding config template

Fix finding config template

Commit 9a73785 ("Better handling icon&config.xml to build widget")
seems to have accidentally broken an application providing its own
config template, resulting in the stock templates always being used.
That results in breakage like extra permissions in the app's version
not being picked up.  The logic for setting WIDGET_CONFIG_TEMPLATE
has been reverted to what it was previously to fix the behavior.

Change-Id: I245bc08f466b883b61c286faed933a5e57a74845
Signed-off-by: Scott Murray <scott.murray@konsulko.com>