New: [rhinstaller/anaconda/pulls/421 master] Improve password salt creation (#1229474)

There was some question as to whether /dev/urandom was being used for generating user password salts, this makes it explicit and reuses the same code for the bootloader password generation. Also adds a test for the new function, iutil.encrypt_password Resolves: rhbz#1229474 -- To view this pull request on github, visit https://github.com/rhinstaller/anaconda/pull/421