tools: Fix python string escape warnings for frr-reload.py

tools: Fix python string escape warnings for frr-reload.py

When using a regex (or anything that uses `\?` escapes) in python, raw
strings (`r"content"`) should be used so python doesn't consume the
escapes itself.  Otherwise we get either broken behavior and/or
`SyntaxWarning: invalid escape sequence '\['`

Fixes: 8916953b534f64a7545860ad5b4b36dc2544f33a ("build: fix a few python string escape warnings")
Fixes: https://github.com/FRRouting/frr/issues/16522
Signed-off-by: Donatas Abraitis <donatas@opensourcerouting.org>