* remove missleading " as first character with no closing quote
* use single quotes in output messages (unclutter)
* when writing changes, make output string copy/pasteable my changing '->' to '>'
Introduced in commit f524254 ("Python/ifconfig: T1557: use read/write helpers
to interface with sysfs") migrate all remaining calls to this new helper.
This enables us to have a single debug call and a single place for error
checking.