Merge remote-tracking branch 'remotes/dgilbert/tags/pull-migration-20190123a' into...

Migration pull 2019-01-23

New pages-per-second stat, a new test, and a bunch
of fixes and tidy ups.

# gpg: Signature made Wed 23 Jan 2019 15:54:48 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-20190123a:
  migration: introduce pages-per-second
  vmstate: constify SaveVMHandlers
  tests: add /vmstate/simple/array
  migration/rdma: unregister fd handler
  migration: unify error handling for process_incoming_migration_co
  migration: add more error handling for postcopy_ram_enable_notify
  migration: multifd_save_cleanup() can't fail, simplify
  migration: fix the multifd code when receiving less channels
  Fix segmentation fault when qemu_signal_init fails

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