qemuxml2argvtest: Use internal wrapping of command line arguments

virCommandToString has the possibility to return an already wrapped
string with better format than what we get from the test wrapper script.

The main advantage is that arguments for an option are always on the
same line which makes it more easy to see what changed in a diff and
prevents re-wrapping of the line if a wrapping point moves over the
threshold.

Additionally the used output is the same we have in the VM log file when
a VM is starting.

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

tests/qemuxml2argvdata/pci-autoadd-idx.args

@@ -18,8 +18,7 @@ QEMU_AUDIO_DRV=none \
 -display none \
 -no-user-config \
 -nodefaults \
--chardev socket,id=charmonitor,path=/tmp/lib/domain--1-fdr-br/monitor.sock,\
-server=on,wait=off \
+-chardev socket,id=charmonitor,path=/tmp/lib/domain--1-fdr-br/monitor.sock,server=on,wait=off \
 -mon chardev=charmonitor,id=monitor,mode=control \
 -rtc base=utc \
 -no-shutdown \
@@ -32,8 +31,7 @@ server=on,wait=off \
 -device pci-bridge,chassis_nr=6,id=pci.6,bus=pci.0,addr=0x9 \
 -device pci-bridge,chassis_nr=7,id=pci.7,bus=pci.0,addr=0xa \
 -usb \
--drive file=/var/iso/f18kde.iso,format=raw,if=none,id=drive-ide0-1-0,\
-readonly=on \
+-drive file=/var/iso/f18kde.iso,format=raw,if=none,id=drive-ide0-1-0,readonly=on \
 -device ide-cd,bus=ide.1,unit=0,drive=drive-ide0-1-0,id=ide0-1-0 \
 -vga cirrus \
 -device virtio-balloon-pci,id=balloon0,bus=pci.4,addr=0x6