Sometimes the tests in the addrmanager_internal_test will fail with:
"addrmanager_internal_test.go: expected to find 5 addresses, found 4"
This is because the generated address with randAddr() may not always
generate an address that's routable. If the address is not routable,
that address will not be added to the manager when calling AddAddress().
This bug is fixed by creating a new function routableRandAddr() that
always creates a routable random address.
In this commit, we update the serialized version of the AddressManager
to also store each address' service bits. This allows an address'
service bits to be properly set when read from disk, which allows
external callers to reliably filter out addresses which do not support
their required services.
Since the service bits were not previously stored, the serialization
version needed to be bumped. A test has been added to test the behavior
of upgrading from version 1 to 2.
