Add http protocol support for cdrom disk

QEMU/KVM already allows a HTTP URL for the cdrom ISO image so add this support
to libvirt as well.
The xml should be as following:

    <disk type='network' device='cdrom'>
      <source protocol='http' name='/url/path'>
        <host name='host.name' port='80'/>
      </source>
    </disk>

Signed-off-by: Aline Manera <alinefm@br.ibm.com>

tests/qemuxml2argvdata/qemuxml2argv-disk-cdrom-network-http.args

@@ -0,0 +1,6 @@
+LC_ALL=C PATH=/bin HOME=/home/test USER=test LOGNAME=test /usr/bin/kvm -S \
+-M pc-1.2 -m 1024 -smp 1 -nographic -nodefaults \
+-monitor unix:/tmp/test-monitor,server,nowait -boot d -usb \
+-drive file=http://host.name:80/url/path/file.iso,if=none,media=cdrom,id=drive-ide0-1-0 \
+-device ide-drive,bus=ide.1,unit=0,drive=drive-ide0-1-0,id=ide0-1-0 \
+-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3

tests/qemuxml2argvdata/qemuxml2argv-disk-cdrom-network-http.xml

@@ -0,0 +1,37 @@
+<domain type='kvm'>
+  <name>QEMUGuest1</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>1048576</memory>
+  <currentMemory unit='KiB'>1048576</currentMemory>
+  <vcpu placement='static'>1</vcpu>
+  <os>
+    <type arch='x86_64' machine='pc-1.2'>hvm</type>
+    <boot dev='cdrom'/>
+  </os>
+  <features>
+    <acpi/>
+    <apic/>
+    <pae/>
+  </features>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>restart</on_crash>
+  <devices>
+    <emulator>/usr/bin/kvm</emulator>
+    <disk type='network' device='cdrom'>
+      <driver name='qemu' type='raw'/>
+      <source protocol='http' name='/url/path/file.iso'>
+        <host name='host.name' port='80'/>
+      </source>
+      <target dev='hdc' bus='ide'/>
+      <readonly/>
+      <alias name='ide0-1-0'/>
+      <address type='drive' controller='0' bus='1' target='0' unit='0'/>
+    </disk>
+    <controller type='usb' index='0'/>
+    <controller type='pci' index='0' model='pci-root'/>
+    <controller type='ide' index='0'/>
+    <memballoon model='virtio'/>
+  </devices>
+</domain>

tests/qemuxml2argvtest.c

@@ -443,6 +443,8 @@ mymain(void)
     DO_TEST("hugepages", QEMU_CAPS_MEM_PATH);
     DO_TEST("nosharepages", QEMU_CAPS_MACHINE_OPT, QEMU_CAPS_MEM_MERGE);
     DO_TEST("disk-cdrom", NONE);
+    DO_TEST("disk-cdrom-network-http", QEMU_CAPS_KVM, QEMU_CAPS_DEVICE,
+            QEMU_CAPS_DRIVE);
     DO_TEST("disk-cdrom-empty", QEMU_CAPS_DRIVE);
     DO_TEST("disk-cdrom-tray",
             QEMU_CAPS_DRIVE, QEMU_CAPS_DEVICE, QEMU_CAPS_VIRTIO_TX_ALG);