* New upstream snapshot. - Drop Precise from vmtest - clear_holders: bcache log IO/OS exceptions but do not raise - vmtest: Support newer qemu and multipath. - block: enable control over exclusive_open use when wiping volumes - block: handle wiping bcache parts (LP: #1718699) - vmtests: Defer ArtfulNetworkMtu SkipbyDate to 2018 - bcache: accept sysfs write failure in shutdown handler if path missing (LP: #1700564) - vmtest: Rephrase a message about no disks to be less scary - block_meta: use block.wipe_volume(mode=superblock) to clear MBR/GPT tables (LP: #1722322)