scripts/qemustart: no network by default and enable with -n

This should make it easier to set up and possibly provide a "work out of
the box" experience for most test usage.  Typical wan&lan networking
setup is only two characters argument away.

Cc: Petr Štetiar <ynezz@true.cz>
Signed-off-by: Yousong Zhou <yszhou4tech@gmail.com>
Acked-by: Hans Dedecker <dedeckeh@gmail.com>

scripts/qemustart

@@ -74,7 +74,7 @@ check_setup_() {
 }
 
 check_setup() {
-	[ -z "$o_nonetwork" ] || return 0
+	[ -n "$o_network" ] || return 0
 	check_setup_ || {
 		__errmsg "please check the script content to see the environment requirement"
 		return 1
@@ -90,6 +90,7 @@ Usage: $SELF [-h|--help]
          [--kernel <kernel>]
          [--rootfs <rootfs>]
          [--machine <machine>]
+         [-n|--network]
 
 <subtarget> will default to "generic" and must be specified if
 <extra-qemu-options> are present
@@ -120,13 +121,14 @@ rand_mac() {
 }
 
 parse_args() {
+	o_network=
 	o_qemu_extra=()
 	while [ "$#" -gt 0 ]; do
 		case "$1" in
-			--no-network|-n) o_nonetwork=1; shift ;;
 			--kernel) o_kernel="$2"; shift 2 ;;
 			--rootfs) o_rootfs="$2"; shift 2 ;;
 			--machine|-machine|-M) o_mach="$2"; shift 2 ;;
+			--network|-n) o_network=1; shift ;;
 			--help|-h)
 				usage
 				exit 0
@@ -187,7 +189,7 @@ start_qemu_armvirt() {
 		)
 	}
 
-	[ -n "$o_nonetwork" ] || {
+	[ -z "$o_network" ] || {
 		o_qemu_extra+=( \
 			"-netdev" "bridge,id=lan,br=$BR_LAN,helper=$HELPER" \
 			    "-device" "virtio-net-pci,id=devlan,netdev=lan,mac=$MAC_LAN" \
@@ -229,7 +231,7 @@ start_qemu_malta() {
 	# NOTE: order of wan, lan -device arguments matters as it will affect which
 	# one will be actually used as the wan, lan network interface inside the
 	# guest machine
-	[ -n "$o_nonetwork" ] || {
+	[ -z "$o_network" ] || {
 		o_qemu_extra+=( \
 			"-netdev" "bridge,id=wan,br=$BR_WAN,helper=$HELPER" "-device" \
 			    "virtio-net-pci,id=devwan,netdev=wan,mac=$MAC_WAN" \
@@ -276,7 +278,7 @@ start_qemu_x86() {
 	    )
 	}
 
-	[ -n "$o_nonetwork" ] || {
+	[ -z "$o_network" ] || {
 		o_qemu_extra+=( \
 			"-netdev" "bridge,id=lan,br=$BR_LAN,helper=$HELPER" \
 			    "-device" "virtio-net-pci,id=devlan,netdev=lan,mac=$MAC_LAN" \