wifi: Use new API for wifi data usage function

For wifi, a old API: buildTemplateWifiWildcard will includes the merged
wifi which is included to mobile usage. It should not double count
again. Call new API: buildTemplateWifi with
NetworkId: NetworkTemplate.WIFI_NETWORKID_ALL
and null subscriberId to get non-merged wifi usage.

Test: atest -c DataUsageControllerTest
Test: Manual Test, wifi data usage count correctly.
Bug: 176396812
Change-Id: I047bc7dfe6a217c1a88faf3ed5c6783f33227c32