Remove code handling the QEMU_CAPS_DOMID capability

This option is xenner-only (since commit b81a7ece),
and we dropped support for xenner in commit de9be0ab.

src/qemu/qemu_command.c

@@ -8449,10 +8449,7 @@ qemuBuildCommandLine(virConnectPtr conn,
     if (def->virtType == VIR_DOMAIN_VIRT_XEN ||
         STREQ(def->os.type, "xen") ||
         STREQ(def->os.type, "linux")) {
-        if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_DOMID)) {
-            virCommandAddArg(cmd, "-domid");
-            virCommandAddArgFormat(cmd, "%d", def->id);
-        } else if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_XEN_DOMID)) {
+        if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_XEN_DOMID)) {
             virCommandAddArg(cmd, "-xen-attach");
             virCommandAddArg(cmd, "-xen-domid");
             virCommandAddArgFormat(cmd, "%d", def->id);

tests/qemuxml2argvtest.c

@@ -287,9 +287,6 @@ static int testCompareXMLToArgvFiles(const char *xml,
         goto out;
     }
 
-    if (virQEMUCapsGet(extraFlags, QEMU_CAPS_DOMID))
-        vmdef->id = 6;
-    else
     vmdef->id = -1;
 
     memset(&monitor_chr, 0, sizeof(monitor_chr));

tests/qemuxmlnstest.c

@@ -84,9 +84,6 @@ static int testCompareXMLToArgvFiles(const char *xml,
             goto fail;
     }
 
-    if (virQEMUCapsGet(extraFlags, QEMU_CAPS_DOMID))
-        vmdef->id = 6;
-    else
     vmdef->id = -1;
 
     memset(&monitor_chr, 0, sizeof(monitor_chr));