WifiNetworkAgentSpecifier: Allow satisfiedBy call for 2 instances

The specifier created for wifi network agent will end up being compared
with itself whenever there is a capability update sent for example.

Test: ./frameworks/base/wifi/tests/runtests.sh
Test: act.py -c wifi_manager.config -tb dut-name -tc WifiManagerTest
Change-Id: Id8c28fd96ac298df2c17f94476abf9cdbc5d23c9