Remove Network::Type and Network::getType()

Enumeration Network::Type and member function Network::getType() can be
removed after aosp/1657760. Specializations of each type of network are
implemented in subclass. No functionality changes.

Test: atest
Change-Id: Ib57bf26e4f0a60f7f01bec3109fb84458fb3abfb
13 files changed