common: hide internal logger configuration strings from clients

common: hide internal logger configuration strings from clients

Replace the common pattern used by clients of the logger, of:
- creating multiple "one element maps" for all config options;
- passing them, untouched, to the logger's update config.
with one that hides the configuration handling details from
the users.

Note: a followup PR, bypassing the strmaps construction altogether,
should be considered.

Signed-off-by: Ronen Friedman <rfriedma@redhat.com>