pathd, tools: fix peer preference config

pathd, tools: fix peer preference config

on one hand, the default value for a peer preference was always being
displayed, and on the other there was some code in frr-reload.py which
was attempting to add a default value to match this behavior, and which
was incorrectly overriding a specified preference. Fix this by removing
this code and making pathd behave like other daemons in this respect,
i.e. not displaying the default value.

Signed-off-by: Emanuele Di Pascale <emanuele@voltanet.io>