remove LDAP depenency

[belforte]

DagmanCreator uses LDAP to get content of e-group highPrioUsers
But that can be pulled from CRIC with an HTTP call https://cms-cric.cern.ch/api/accounts/group/query/?json
(maybe there's a way to retrieve only that group ?)

that should allow deprecating

CRABServer/src/python/CMSGroupMapper.py

Line 20 in 9812df1

def get_egroup_users(egroup_name):

and hence to remove dependency from LDAP