* cfg.mk (useless_free_options): Add many vir*Free* function names,
and then remove the useless if-before-free tests exposed by running
make syntax-check.
* src/conf/interface_conf.c (virInterfaceDefFree): Remove useless "if".
(virInterfaceAssignDef): Likewise.
* src/conf/network_conf.c (virNetworkAssignDef): Likewise.
* src/conf/storage_conf.c (virStoragePoolObjAssignDef): Likewise.
* src/node_device/node_device_hal.c (dev_create): Likewise.
* src/security/virt-aa-helper.c (vahDeinit): Likewise.
* src/test/test_driver.c (testNodeDeviceCreateXML): Likewise.
* src/util/conf.c (virConfSetValue): Likewise.