IMPALA-7995: part 1: fixes for e2e dockerised impala tests

This fixes all core e2e tests running on my local dockerised
minicluster build. I do not yet have a CI job or script running
but I wanted to get feedback on these changes sooner. The second
part of the change will include the CI script and any follow-on
fixes required for the exhaustive tests.

The following fixes were required:
* Detect docker_network from TEST_START_CLUSTER_ARGS
* get_webserver_port() does not depend on the caller passing in
  the default webserver port. It failed previously because it
  relied on start-impala-cluster.py setting -webserver_port
  for *all* processes.
* Add SkipIf markers for tests that don't make sense or are
  non-trivial to fix for containerised Impala.
* Support loading Impala-lzo plugin from host for tests that depend on
  it.
* Fix some tests that had 'localhost' hardcoded - instead it should
  be $INTERNAL_LISTEN_HOST, which defaults to localhost.
* Fix bug with sorting impala daemons by backend port, which is
  the same for all dockerised impalads.

Testing:
I ran tests locally as follows after having set up a docker network and
starting other services:

  ./buildall.sh -noclean -notests -ninja
  ninja -j $IMPALA_BUILD_THREADS docker_images
  export TEST_START_CLUSTER_ARGS="--docker_network=impala-cluster"
  export FE_TEST=false
  export BE_TEST=false
  export JDBC_TEST=false
  export CLUSTER_TEST=false
  ./bin/run-all-tests.sh

Change-Id: Iee86cbd2c4631a014af1e8cef8e1cd523a812755
Reviewed-on: http://gerrit.cloudera.org:8080/12639
Reviewed-by: Joe McDonnell <joemcdonnell@cloudera.com>
Tested-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>

tests/hs2/test_fetch_first.py

@@ -32,7 +32,7 @@ class TestFetchFirst(HS2TestSuite):
   def __test_invalid_result_caching(self, sql_stmt):
     """ Tests that invalid requests for query-result caching fail
     using the given sql_stmt."""
-    impala_cluster = ImpalaCluster()
+    impala_cluster = ImpalaCluster.get_e2e_test_cluster()
     impalad = impala_cluster.impalads[0].service
 
     execute_statement_req = TCLIService.TExecuteStatementReq()