Treat pwd is not set if no entry in shadow for usr

There are situations (mostly manipulated), when user entry is present
in /etc/password, but not in /etc/shadow. Even though user can’t login
without proper entry in /etc/shadow, it is a valid user and password
update is only required

Tested:
1. Manually removed a user entry in /etc/shadow
2. Restarted phosphor-user-manager service
3. Made sure user is listed, and able to update the password through
   ipmitool set password command
4. Queried the user entry again and confirmed PasswordExpired is
   returned as false.

Signed-off-by: Jayaprakash Mutyala <mutyalax.jayaprakash@intel.com>
Change-Id: I818be9a63121448210a99c175005708788279963
1 file changed