pam_pwhistory enforces root to password change history when resetting non-root user's password

Issue

When pam_pwhistory is in use root is forced to pick a password not in user's history when changing user's password.

For example:
- insert the following in /etc/pam.d/system-auth-ac (after pam_cracklib.so line if present)

password    requisite     pam_pwhistory.so remember=6 use_authtok

• Attempt to change the passowrd of a normal user.

[root@rhel57 ~]# passwd test
<Enter already used password>

Actual results:

Changing password for user test.
New UNIX password: 
Retype new UNIX password: 
Password has been already used. Choose another.
passwd: Have exhausted maximum number of retries for service

Expected results:

Changing password for user test.
New UNIX password: 
Retype new UNIX password: 
Password has been already used.
passwd: all authentication tokens updated successfully.