net: Avoid qerror_report_err() outside QMP command handlers

net: Avoid qerror_report_err() outside QMP command handlers

qerror_report_err() is a transitional interface to help with
converting existing monitor commands to QMP.  It should not be used
elsewhere.  Replace by error_report_err() in HMP command handler
hmp_host_net_add() and initial startup helpers net_init_client(),
net_init_netdev().  Keep it in QMP command handler qmp_netdev_add().

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>