virRaiseErrorLog: Don't skip error printing when enabling debug logging env variable

virRaiseErrorLog: Don't skip error printing when enabling debug logging env variable

When a user requests debug logging by setting the environment variable:

LIBVIRT_DEBUG=1

we should log any errors regardless of the setting of e.g.
'LIBVIRT_LOG_OUTPUTS' as the code will log every 'debug' and 'info'
level message to stderr but will skip 'error' level messages.

This obviously makes debugging things very complicated as you can get to
a situation when the error itself is missing.

This can happen e.g. in tests.

Fix the issue by probing the default log level and calling the logger if
it's set for VIR_LOG_DEBUG.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>