Merge remote-tracking branch 'remotes/dgilbert/tags/pull-migration-20201102a' into staging

Migration and virtiofs fixes 2020-11-02

Fixes for postcopy migration test hang
A seccomp crash for virtiofsd on some !x86
Help message and minor CID fix

And another crack at Max's set.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

# gpg: Signature made Mon 02 Nov 2020 19:54:59 GMT
# gpg:                using RSA key 45F5C71B4A0CB7FB977A9FA90516331EBC5BFDE7
# gpg: Good signature from "Dr. David Alan Gilbert (RH2) <dgilbert@redhat.com>" [full]
# Primary key fingerprint: 45F5 C71B 4A0C B7FB 977A  9FA9 0516 331E BC5B FDE7

* remotes/dgilbert/tags/pull-migration-20201102a:
  tests/acceptance: Add virtiofs_submounts.py
  tests/acceptance/boot_linux: Accept SSH pubkey
  virtiofsd: Announce sub-mount points
  virtiofsd: Add mount ID to the lo_inode key
  meson.build: Check for statx()
  virtiofsd: Add attr_flags to fuse_entry_param
  virtiofsd: Check FUSE_SUBMOUNTS
  virtiofsd: Fix the help message of posix lock
  tools/virtiofsd: Check vu_init() return value (CID 1435958)
  virtiofsd: Seccomp: Add 'send' for syslog
  migration: Postpone the kick of the fault thread after recover
  migration: Unify reset of last_rb on destination node when recover

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>