Coverity: Fix resource leak in test driver

Error: RESOURCE_LEAK:
/builddir/build/BUILD/libvirt-0.9.10/src/test/test_driver.c:1041: alloc_arg: Calling allocation function "virXPathNodeSet" on "devs".
/builddir/build/BUILD/libvirt-0.9.10/src/util/xml.c:621: alloc_arg: "virAllocN" allocates memory that is stored into "*list".
/builddir/build/BUILD/libvirt-0.9.10/src/util/memory.c:129: alloc_fn: Storage is returned from allocation function "calloc".
/builddir/build/BUILD/libvirt-0.9.10/src/util/memory.c:129: var_assign: Assigning: "*((void **)ptrptr)" = "calloc(count, size)".
/builddir/build/BUILD/libvirt-0.9.10/src/util/xml.c:625: noescape: Variable "*list" is not freed or pointed-to in function "memcpy".
/builddir/build/BUILD/libvirt-0.9.10/src/test/test_driver.c:1098: leaked_storage: Variable "devs" going out of scope leaks the storage it points to.
(cherry picked from commit ad4d4ad0)

src/test/test_driver.c

@@ -1087,6 +1087,7 @@ static int testOpenFromFile(virConnectPtr conn,
     VIR_FREE(networks);
     VIR_FREE(ifaces);
     VIR_FREE(pools);
+    VIR_FREE(devs);
     virDomainObjListDeinit(&privconn->domains);
     virNetworkObjListFree(&privconn->networks);
     virInterfaceObjListFree(&privconn->ifaces);