IMPALA-3238: avoid log spam for very large hash tables
IMPALA-3238: avoid log spam for very large hash tables

Before this change, every time the limit was hit in ConsumeMemory() was
hit, a warning message with stack trace was logged. The streaming preagg
calls this once per partition per batch, resulting in an enormous volume
of logging.

The fix is to log the warning only once for each client (i.e. each exec
node).

We need a very large data set to reproduce this error. To test it
manually I lowered the threshold to 1 << 19, ran 'select distinct
l_orderkey from tpch_20_parquet', and confirmed that only two warning
messages per query appeared in the logs (one per agg node).

Change-Id: I366ce1148e83ac2eb71535d552bc68cb08388eec
Reviewed-on: http://gerrit.cloudera.org:8080/2659
Reviewed-by: Tim Armstrong <2f8e34250f03a653da3dc27f7ec203eafdde80fc@cloudera.com>
Tested-by: Tim Armstrong <2f8e34250f03a653da3dc27f7ec203eafdde80fc@cloudera.com>

cloudera/Impala,michaelhkw/incubator-impala,michaelhkw/incubator-impala,cloudera/Impala,cloudera/Impala,cloudera/Impala,michaelhkw/incubator-impala,michaelhkw/incubator-impala,cloudera/Impala,cloudera/Impala,michaelhkw/incubator-impala,michaelhkw/incubator-impala,michaelhkw/incubator-impala,cloudera/Impala