Automatically set IPsec tunnel interface as up

This change makes IPsec tunnel interfaces automatically get brought up
once they are created. Originally this was considered to be an
additional safety check, as they would not be start routing traffic
until explicitly brought up. However, in the intervening time, the
NetworkManagementController now requires the NETWORK_STACK permission to
set an interface as up. Additionally, that call is a hidden API, and
thus not usable for use cases such as IWLAN.

Bug: 149348618
Test: FrameworksNetTests, CtsNetTestCases passing.
Change-Id: I55b63a748463a388e1e2991d2d5d6b3023545e60