migration/postcopy: Recognise the recovery states as 'in_postcopy'

migration/postcopy: Recognise the recovery states as 'in_postcopy'

Various parts of the migration code do different things when they're
in postcopy mode; prior to this patch this has been 'postcopy-active'.
This patch extends 'in_postcopy' to include 'postcopy-paused' and
'postcopy-recover'.

In particular, when you set the max-postcopy-bandwidth parameter, this
only affects the current migration fd if we're 'in_postcopy';
this leads to a race in the postcopy recovery test where it increases
the speed from 4k/sec to unlimited, but that increase can get ignored
if the change is made between the point at which the reconnection
happens and it transitions back to active.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <20190923174942.12182-1-dgilbert@redhat.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>