daemon: Fix option -v missing info priority log

daemon: Fix option -v missing info priority log

Introduce by 63fbcc692.

When start libvirtd with commandline "/usr/sbin/libvirtd -d -l -v",
we expect verbose(info level) log if neither environment variable
nor config file about logging controls is set. But in fact we can't
get any info priority log in the default output file.

The log priority of default output is VIR_LOG_DEFAULT(VIR_LOG_WARN),
so the info log is filtered out.
To record info priority log we must parse option -v before setting the
default output.

After this patch, we get all verbose log in the default output file.

Signed-off-by: Zhou Yimin <zhouyimin@huawei.com>