In the past, curtin log lines had the syslog identifier matching
"curtin_log.xxx". Nowadays, curtin commands are started via
systemd-run so they end up inheriting from the default
"subiquity_log.xxx" syslog identifier.
When updating the examples/curtin-*.json files, one must make sure to
filter out the entries that have the "subiquity_log.xxx" but are not
related to curtin invocations.
In the future, maybe we need to consider overriding the syslog
identifier when invoking curtin commands.
Signed-off-by: Olivier Gayot <olivier.gayot@canonical.com>