IMPALA-7643: report # queries actually executing in stress test
IMPALA-7643: report # queries actually executing in stress test

With admission control it's interesting to separate out two categories
of queries:
1. Queries that have started up and are executing
2. Queries that have not made it that far yet, e.g. are waiting to
  establish a client connection (hitting --fe_service_threads limit),
  are in the planner, are queued in admission control or are starting
  up.

We now call 1+2 "Active" and 1 "Executing".

Example output:
Done | Active | Executing | Mem Lmt Ex | AC Reject | AC Timeout | Time Out | Cancel | Err | Incorrect | Next Qry Mem Lmt | Tot Qry Mem Lmt | Tracked Mem | RSS Mem
   0 |      0 |         0 |          0 |         0 |          0 |        0 |      0 |   0 |         0 |                0 |               0 |             |
   0 |     10 |         3 |          0 |         0 |          0 |        0 |      0 |   0 |         0 |              510 |            3922 |         158 |    4541
   0 |     20 |        10 |          0 |         0 |          0 |        0 |      0 |   0 |         0 |              390 |            8534 |         570 |    4517

Refactored QueryRunner.run_query() to reduce nesting and make it more
readable.

Testing:
Ran local stress tests with and without --test_admission_control set.

Change-Id: I5692e8e5ba3224becefc24437197bf5a5b450335
Reviewed-on: http://gerrit.cloudera.org:8080/11587
Reviewed-by: Impala Public Jenkins <039b6b20426ff68ebe492b3021890d8c8fd010c9@cloudera.com>
Tested-by: Impala Public Jenkins <039b6b20426ff68ebe492b3021890d8c8fd010c9@cloudera.com>

cloudera/Impala,cloudera/Impala,cloudera/Impala,cloudera/Impala,cloudera/Impala,cloudera/Impala,cloudera/Impala