Logger no longer errors when logfile path is invalid SCMSUITE-9740 SO107

[dormrod]

Description

Couple of small fixes/tweaks to the logger class.

• Do not error if the logfile path is invalid (i.e. directory does not exist). This was also the previous plams behaviour so was an accidental regression
• Use abspaths when comparing whether the logfile handler should be updated. This avoids recreating the handler too frequently when using relative paths