Index maintenance function for BRIN doesn't check RecoveryInProgress()

Hi,

Three functions: brin_summarize_new_values, brin_summarize_range and
brin_desummarize_range can be called during recovery as follows.

=# select brin_summarize_new_values('a_idx');
ERROR: cannot acquire lock mode ShareUpdateExclusiveLock on database
objects while recovery is in progress
HINT: Only RowExclusiveLock or less can be acquired on database
objects during recovery.

I think we should complaint "recovery is in progress" error in this
case rather than erroring due to lock modes.
Attached patch fixes them.

Regards,

--
Masahiko Sawada
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center