lib: Allow zclient do-over of connect on initial attempt

lib: Allow zclient do-over of connect on initial attempt

When a protocol is attempting to connect to the zebra daemon
through it's socket.  If the inital attempt fails, give it a
few more attempts before giving up and leaving the daemon in
a bizarre state.

This problem was found by Ashley Penney, and Ashley was of
immense help in debugging and testing the fix for this issue.

Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>
Tested-by: Ashley Penney <apenney@ntoggle.com>