mon: LogMonitor: handle boolean options consistently

mon: LogMonitor: handle boolean options consistently

'mon_cluster_log_to_syslog' gets a string of key/value pairs, values
in the pair being booleans, and keys being optional (one can simply
specify the value). However, we weren't being consistent with the
boolean behavior when handling option values. e.g., the user expects
'1' and '0' to mean 'true' and 'false' respectively, and expects
'mon_cluster_log_to_syslog' to understand both '1' and '0', alongside
with 'true' and 'false'.

All values not 'true' or '1' will be considered 'false'.

Fixes: #12325
Signed-off-by: Joao Eduardo Luis <joao@suse.de>