Usage Settings: Fix NPE when subscriberId is Null.

For mobile, a old API: buildTemplateMobileAll doesn't includes the
merged wifi network, call the new API: buildTemplateCarrierMetered
to replace the old one.

But new API: buildTemplateCarrierMetered requires non-null subscriberId.
Call old API: buildTemplateMobileAll when subscriberId is NULL since
the matched result is always empty when subscriberId is NULL. No any different
between buildTemplateCarrierMetered and buildTemplateMobileAll.

Bug: 190233044
Bug: 190135429
Test: make RunSettingsRoboTests ROBOTEST_FILTER=SettingsDumpServiceTest
Test: make RunSettingsRoboTests ROBOTEST_FILTER=DataUsageLibTest

Change-Id: Ic6dada8260029e47e044d016ebc701c25dbf9b2a