Fix a bug introduced in r399992, where creating only a user would fail
due to $PW not being set. This only occurred when just a user was being
created without a group. Solve this by setting $PW outside of the group
creation and above both the user and group creation parts.

PR: 203489
Reviewed by: bapt
Approved by: portmgr (bapt)
Approved by: bdrewery (mentor)