scrub clears inconsistent flag set by deep scrub

Add new num_deep_scrub_errors and num_shallow_scrub_errors to object_stat_sum_t
Show deep-scrub error count when outputing regular scrub errors
Set invalid size in case of a stat error which sets read_error
For now do deep-scrub after repair (see #4783)

fixes: #4778
Signed-off-by: David Zafman <david.zafman@inktank.com>
Merge branch 'wip-4778' into next

Reviewed-by: Samuel Just <sam.just@inktank.com>