IMPALA-3020: Don't take QueryExecState::lock() needlessly
IMPALA-3020: Don't take QueryExecState::lock() needlessly

ImpalaServer::UpdateFilter() takes QueryExecState::lock(), but doesn't
need to, leading to excessive contention for that lock if UpdateFilter()
takes a long time due to Bloom Filters being large.

Change-Id: Ia252f4dadbd5c4c9ae375e4c9ec8f2862d3bff82
Reviewed-on: http://gerrit.cloudera.org:8080/2221
Reviewed-by: Henry Robinson <3eca10f30041813f045165784e24b5a950a6cc7e@cloudera.com>
Tested-by: Henry Robinson <3eca10f30041813f045165784e24b5a950a6cc7e@cloudera.com>

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