(Re)-allow 0.0.0.0 to be used as an address in connect() for TCP
In r361752 an error handling was introduced for using 0.0.0.0 or
255.255.255.255 as the address in connect() for TCP, since both
addresses can't be used. However, the stack maps 0.0.0.0 implicitly
to a local address and at least two regressions were reported.
Therefore, re-allow the usage of 0.0.0.0.
While there, change the error indicated when using 255.255.255.255
from EAFNOSUPPORT to EACCES as mentioned in the man-page of connect().

Reviewed by: rrs
MFC after: 1 week
Sponsored by: Netflix, Inc.
Differential Revision: https://reviews.freebsd.org/D25401