Fix leak on OOM in qemuBuildCommandLine dealing with sound card

The qemuBuildCommandLine code for parsing sound cards will leak
an intermediate variable if an OOM occurs. Move the free'ing of
the variable earlier to avoid the leak.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

src/qemu/qemu_command.c

@@ -9102,7 +9102,7 @@ qemuBuildCommandLine(virConnectPtr conn,
                         goto error;
 
                     virCommandAddArg(cmd, str);
-
+                    VIR_FREE(str);
                     if (sound->model == VIR_DOMAIN_SOUND_MODEL_ICH6 ||
                         sound->model == VIR_DOMAIN_SOUND_MODEL_ICH9) {
                         char *codecstr = NULL;
@@ -9130,8 +9130,6 @@ qemuBuildCommandLine(virConnectPtr conn,
                             VIR_FREE(codecstr);
                         }
                     }
-
-                    VIR_FREE(str);
                 }
             }
         } else {