Merge remote-tracking branch 'remotes/dgilbert/tags/pull-migration-20180214a' into...

Migration pull 20180214

Note that the 'Add test for migration to bad destination' displays
a 'Connection refused' during running, but still gives the correct exit
code and OK (It's checking that the source doesn't fail when
it can't connect, so that's the right error).
If it's particularly disliked that patch can be skipped individually.

# gpg: Signature made Wed 14 Feb 2018 15:33:04 GMT
# gpg:                using RSA key 0516331EBC5BFDE7
# gpg: Good signature from "Dr. David Alan Gilbert (RH2) <dgilbert@redhat.com>"
# Primary key fingerprint: 45F5 C71B 4A0C B7FB 977A  9FA9 0516 331E BC5B FDE7

* remotes/dgilbert/tags/pull-migration-20180214a:
  migration: pass MigrationState to migrate_init()
  migration: allow send_rq to fail
  migration: provide postcopy_fault_thread_notify()
  migration: reuse mis->userfault_quit_fd
  migration: better error handling with QEMUFile
  tests/migration: Add test for migration to bad destination
  migration: Fix early failure cleanup
  tests/migration: Add source to PC boot block
  migration: improve documentation of postcopy-ram
  migration/xen: Check return value of qemu_fclose

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