tipc: Fix redundant link field handling in link protocol message

tipc: Fix redundant link field handling in link protocol message

Ensures that the "redundant link exists" field of the LINK_PROTOCOL
messages sent by a link endpoint is set if and only if the sending
node has at least one other working link to the peer node. Previously,
the bit was set only if there were at least 2 working links to the peer
node, meaning the bit was incorrectly left unset in messages sent by a
non-working link endpoint when exactly one alternate working link was
available. The revised code now takes the state of the link sending
the message into account when deciding if an alternate link exists.

Signed-off-by: Allan Stephens <Allan.Stephens@windriver.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>