[libvirt] [PATCH]Fix minor issues in logical storage backend

Hi All! I came across some problems trying to create a new LVM-based storage pool using this config <pool type="logical"> <name>test_vg</name> <source> <device path="/dev/sdb1"/> </source> <target> <path>/dev/test_vg</path> </target> </pool> Volume group did not previously exist so I did virsh pool-define <above.xml> virsh pool-build test_vg pool-build failed since the backend logical storage driver does not have VIR_STORAGE_BACKEND_POOL_SOURCE_DEVICE set in flags. Without this flag set, the device element is never parsed in virStoragePoolDefParseDoc() (storage_conf.c), causing pvcreate to fail since no physical volume is specified. After this problem was memory corruption cause by miscalculating the size of vgcreate command line :-). This patch fixes both issues. Regards, Jim