utils: Always specify family and ->bytelen in get_prefix_1()

utils: Always specify family and ->bytelen in get_prefix_1()

Handle default/all/any special case in get_addr_1() to setup
->family and ->bytelen correctly.

Make get_addr_1() return ->bitlen == -2 instead of -1 to
distinguish default/all/any special case from the rest:
it is safe because all callers check ->bitlen < 0, not
explicit value -1.

Reduce intendation by one level and get rid of goto/label
to make code more readable.

Signed-off-by: Serhey Popovych <serhe.popovych@gmail.com>
Signed-off-by: David Ahern <dsahern@gmail.com>