PostgreSQL: create base dir on RAMFS before setup
PostgreSQL: create base dir on RAMFS before setup

See original commit c32c91d2ebbca08a3c309de7a7bb34d87b7cb8b8 in
ha-feature-trusty branch.

vinaykaradia/travis-cookbook-cloned,tianon/travis-cookbooks,spurti-chopra/travis-cookbooks,dracos/travis-cookbooks,vinaykaradia/travis-cookbook-cloned,DanielG/travis-cookbooks,Distelli/travis-cookbooks,travis-ci/travis-cookbooks,vinaykaradia/travis-cookbook-cloned,DanielG/travis-cookbooks,DanielG/travis-cookbooks,vinaykaradia/travis-cookbook-cloned,vinaykaradia/travis-cookbook-cloned,dracos/travis-cookbooks,Distelli/travis-cookbooks,ardock/travis-cookbooks,Zarthus/travis-cookbooks,Acidburn0zzz/travis-cookbooks,DanielG/travis-cookbooks,tianon/travis-cookbooks,Distelli/travis-cookbooks,Zarthus/travis-cookbooks,spurti-chopra/travis-cookbooks,Zarthus/travis-cookbooks,tianon/travis-cookbooks,ljharb/travis-cookbooks,gavioto/travis-cookbooks,ljharb/travis-cookbooks,tianon/travis-cookbooks,Acidburn0zzz/travis-cookbooks,dracos/travis-cookbooks,ljharb/travis-cookbooks,tianon/travis-cookbooks,ardock/travis-cookbooks,ardock/travis-cookbooks,spurti-chopra/travis-cookbooks,ardock/travis-cookbooks,dracos/travis-cookbooks,gavioto/travis-cookbooks,gavioto/travis-cookbooks,Zarthus/travis-cookbooks,travis-ci/travis-cookbooks,travis-ci/travis-cookbooks,Acidburn0zzz/travis-cookbooks,Distelli/travis-cookbooks,Acidburn0zzz/travis-cookbooks,gavioto/travis-cookbooks