vircgroup: extract virCgroupNewDetect from virCgroupNew

The current code uses virCgroupNew() as a single point of entry and
calls into virCgroupDetect() as well. Both have logic for several paths
which is difficult to figure out.

Extract the actually used code path from the two functions to make
it obvious what's happening in this case.

Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>

src/util/vircgroup.c

@@ -1048,7 +1048,28 @@ virCgroupNewDetect(pid_t pid,
                    int controllers,
                    virCgroupPtr *group)
 {
-    return virCgroupNew(pid, "", NULL, controllers, group);
+    g_autoptr(virCgroup) new = g_new0(virCgroup, 1);
+
+    VIR_DEBUG("pid=%lld controllers=%d group=%p",
+              (long long) pid, controllers, group);
+
+    if (virCgroupSetBackends(new) < 0)
+        return -1;
+
+    if (virCgroupDetectMounts(new) < 0)
+        return -1;
+
+    if (virCgroupDetectPlacement(new, pid, "") < 0)
+        return -1;
+
+    if (virCgroupValidatePlacement(new, pid) < 0)
+        return -1;
+
+    if (virCgroupDetectControllers(new, controllers, NULL) < 0)
+        return -1;
+
+    *group = g_steal_pointer(&new);
+    return 0;
 }