lxc: fix starting a domain with a cpuset but no numatune

 # virsh -c lxc:/// start helloworld
 error: Failed to start domain helloworld
 error: internal error: guest failed to start: Invalid value '1-3'
 for 'cpuset.mems': Invalid argument

Free the cpu mask to avoid reusing it as a mem mask
in virCgroupSetCpusetMems
if virDomainNumatuneMaybeFormatNodeset does not set a mask.
Signed-off-by: NLuyao Huang <lhuang@redhat.com>
Signed-off-by: NJán Tomko <jtomko@redhat.com>

src/lxc/lxc_cgroup.c

@@ -77,6 +77,8 @@ static int virLXCCgroupSetupCpusetTune(virDomainDefPtr def,
 
         if (virCgroupSetCpusetCpus(cgroup, mask) < 0)
             goto cleanup;
+        /* free mask to make sure we won't use it in a wrong way later */
+        VIR_FREE(mask);
     }
 
     if (virDomainNumatuneGetMode(def->numa, -1) !=