Fix pw_hash() on JRuby < 1.7.17

The previous change to this function broke it on JRuby before 1.7.17 by
attempting to use a variable that wasn't defined (`salt`). To fix this,
define `salt` ahead of time and use that instead of building the salt
later.

cf. http://git.io/vJ9e7

lib/puppet/parser/functions/pw_hash.rb

@@ -38,6 +38,8 @@
  password = args[0]
  return nil if password.nil? or password.empty?
 
+ salt = "$#{hash_type}$#{args[2]}"
+
  # handle weak implementations of String#crypt
  if 'test'.crypt('$1$1') != '$1$1$Bp8CU9Oujr9SSEw53WV6G.'
  # JRuby < 1.7.17
@@ -49,6 +51,6 @@
  raise Puppet::ParseError, 'system does not support enhanced salts'
  end
  else
- password.crypt("$#{hash_type}$#{args[2]}")
+ password.crypt(salt)
  end
 end