Changed cucumber user test

For some reason when running rails 3.2.8 with ruby 1.8 on travis,
validation if password is blank returns only message:
Must be a unique password with at least 4 character and at most 255 characters.

Although the test passes unchanged for ruby 1.9.

(cherry picked from commit 3bebbdd3e98023164d2ede1d96c92851e6724fba)
Merge pull request #296 from jistr/fix_travis_ruby18

Fix Travis 1.8 cucumber