Merge remote-tracking branch 'remotes/stefanha/tags/tracing-pull-request' into staging

Merge remote-tracking branch 'remotes/stefanha/tags/tracing-pull-request' into staging

# gpg: Signature made Mon 16 Jan 2017 13:44:46 GMT
# gpg:                using RSA key 0x9CA4ABB381AB73C8
# gpg: Good signature from "Stefan Hajnoczi <[email protected]>"
# gpg:                 aka "Stefan Hajnoczi <[email protected]>"
# Primary key fingerprint: 8695 A8BF D3F9 7CDA AC35  775A 9CA4 ABB3 81AB 73C8

* remotes/stefanha/tags/tracing-pull-request:
  trace: Add event "guest_cpu_exit"
  trace: Fix dynamic event state on vCPU hot-unplug
  trace: Lock vCPU list when initializing dynamic tracing state
  trace-events: spelling fix

Signed-off-by: Peter Maydell <[email protected]>