qemu: process: Set current vcpu count to maximum if it was not specified

Mimic qemu's behavior on the given command line.

src/qemu/qemu_parse_command.c

@@ -1725,6 +1725,9 @@ qemuParseCommandLineSmp(virDomainDefPtr dom,
     if (maxcpus == 0)
         goto syntax;
 
+    if (vcpus == 0)
+        vcpus = maxcpus;
+
     if (virDomainDefSetVcpusMax(dom, maxcpus, xmlopt) < 0)
         goto error;