[PDI-11582] HDP 2.1 Linux Shim Support (Unsecure)

Remove upsupported hdp20 shim
PDI-12582 - Sqoop Import/Export Dialogs`s database selection "Use Advanced Options" cause null pointer exception - handle ADVANCED_LIST mode
[BACKLOG-350] Fixes the tests so that the reducers are closed and their buffer empties before the assertions are done.
Merge pull request #239 from pavel-sakun/PDI-11582-remove-hdp20

[PDI-11582] HDP 2.1 Linux Shim Support (Unsecure)
Merge pull request #246 from lucboudreau/master

[BACKLOG-350] Fixes the tests so that the reducers are closed and their ...
[BACKLOG-115] Certify support for Kerberos for CDH 5.1

Add cdh51 shim
Merge pull request #240 from akhayrutdinov/PDI-12582

[PDI-12582] - Sqoop Import/Export Dialogs`s database selection "Use Advanced Options" cause null pointer exception
Merge pull request #242 from TatsianaKasiankova/BACKLOG-331

[BACKLOG-331]: CLONE - Spoon Fails to start if the designated shim doesn't load properly
Merge pull request #247 from pavel-sakun/BACKLOG-115

[BACKLOG-115] Certify support for Kerberos for CDH 5.1
[BACKLOG-331][CHECKSTYLE]: CLONE - Spoon Fails to start if the designated shim doesn't load properly

Checkstyle fixes for unit test.