lxc: fix starting a domain with non-strict numa memory mode

 # virsh -c lxc:/// start helloworld
 error: Failed to start domain helloworld
 error: internal error: guest failed to start: Unknown
 failure in libvirt_lxc startup

Return success when there are no cpuset.mems to be set,
instead of failing without setting an error.
Signed-off-by: NJán Tomko <jtomko@redhat.com>

src/lxc/lxc_cgroup.c

@@ -82,8 +82,10 @@ static int virLXCCgroupSetupCpusetTune(virDomainDefPtr def,
     }
 
     if (virDomainNumatuneGetMode(def->numa, -1) !=
-        VIR_DOMAIN_NUMATUNE_MEM_STRICT)
+        VIR_DOMAIN_NUMATUNE_MEM_STRICT) {
+        ret = 0;
         goto cleanup;
+    }
 
     if (virDomainNumatuneMaybeFormatNodeset(def->numa, nodemask,
                                             &mask, -1) < 0)