Increase the amount of salt crypt_pwd generates

[jasonborden]

Is your feature request related to a problem? Please describe.
Salt currently generated by crypt_pwd is only 12 bits which is rather weak

Describe the solution you'd like
Make the amount of salt generated the same as linux shadow

Describe alternatives you've considered
A way for the user to configure the amount of salt generated would also work, but is not currently possible.

Additional context
https://lists.fedorahosted.org/archives/list/freeipa-users@lists.fedorahosted.org/thread/ZJXVFQ6XC2IEROA2LZNBXKQ6YWAJHAIU/

[jasonborden]

Issue is resolved with merged commit.