clang-tidy: disable misc-non-private-member-variables-in-classes entirely
clang-tidy: disable misc-non-private-member-variables-in-classes entirely

This diagnostic emits many warnings about protected data members in test
fixtures, which are required for some advanced gtest usage.

Change-Id: Ife21645ef45e84e75e0746f280ec6d06e37e38cf
Reviewed-on: http://gerrit.cloudera.org:8080/15003
Tested-by: Kudu Jenkins
Reviewed-by: Alexey Serbin <864f6b82bd94e8dda64141d4274519ee66e0102e@cloudera.com>
Reviewed-by: Andrew Wong <b68e4fdc6430321a6b47400732ff97d7ae91234e@cloudera.com>

helifu/kudu,helifu/kudu,helifu/kudu,helifu/kudu,helifu/kudu,helifu/kudu,helifu/kudu,helifu/kudu,helifu/kudu