Don't require ACCESS_NETWORK_STATE in setProcessDefaultNetwork

The documentation for setProcessDefaultNetwork does not
mention that it requires ACCESS_NETWORK_STATE, but a process
without ACCESS_NETWORK_STATE that calls it will crash because
we can't fetch the proxy properties.

Because ACCESS_NETWORK_STATE is not required to obtain a Network
object (Network objects can come from broadcasts too), it may not
be reasonable to require the permission. We did not do so in L.

For now, ignore the failure and don't crash the app. I've filed
http://b/20470604 to track a longer term fix.

Bug: 20081183
Bug: 20423580
Bug: 20470604
Change-Id: I158016130b4afb1d300357fe703804d2e7bc609b