libpdx_uds: Improve client connection logic

Handle the case where the service created a socket file but not bound the
socket to it, or not listening for incoming requests yet. Also, if the service
has crashed and left the socket file behind, need to make sure we reconnect
once the service is restarted.

Bug: None
Test: `m -j32` succeeds, device boots and CubeSea app works on Sailfish
Change-Id: I2039cfca6faccd5d1d4b725e454075669484b880