Bug: Handling of members with different classifications

[astrochun]

Describe the bug (REQUIRED)
The quota.ual_ldap_quota_query ldap3 query strings will return faculty, grad and ugrad members. However, there is overlaps between these groups (e.g., a grad member can also be staff). To fix this issue, it's best to mutually exclusive with the highest rank determining the quota level.

Version information (please complete the following, default in brackets): (REQUIRED)

• ReQUIAM version: 0.12.2`
• ReQUIAM branch info: feature/limited_set

Reproduction Steps (REQUIRED)

from requiam import quota                                                                                                                
from requiam import ldap_query                                                                                                           

# Get query string
grad = quota.ual_ldap_quota_query('grad')
faculty = quota.ual_ldap_quota_query('faculty') 
ugrad = quota.ual_ldap_quota_query('ugrad')

ldc = ldap_query.LDAPConnection(ldap_host='eds.iam.arizona.edu',
                                ldap_base_dn='dc=eds,dc=arizona,dc=edu',
                                ldap_user='**override**', ldap_password='**override**')

# Query for members
faculty_uaid = ldap_query.ldap_search(ldc, faculty)                                                                                      
grad_uaid = ldap_query.ldap_search(ldc, grad)
ugrad_uaid = ldap_query.ldap_search(ldc, ugrad)

# Info
In [10]: len(faculty_uaid)                                                                                                                       
Out[10]: 23558

In [11]: len(grad_uaid)                                                                                                                          
Out[11]: 15450

In [19]: len(ugrad_uaid)                                                                                                                         
Out[19]: 46777

In [13]: len(faculty_uaid & grad_uaid)                                                                                                                            
Out[13]: 860

In [17]: len(faculty_uaid & ugrad_uaid)                                                                                                              
Out[17]: 435

In [18]: len(grad_uaid & ugrad_uaid)                                                                                                             
Out[18]: 4217

Expected behavior (Optional)
Exclusive list for grad and ugrad

[astrochun]

Note: Testing with faculty, grad, and ugrad demonstrated complete exclusion so that grad is a clean list not including faculty and ugrad does not include grad and faculty