always get PAC for client principal if AS_REQ is true
    
    This patch proposes a fix for the following defect reported by covscan in
    FreeIPA master code:
    
    """
    Error: DEADCODE (CWE-561):
    /daemons/ipa-kdb/ipa_kdb_mspac.c:2013: assignment: Assigning: "client_entry" =
    "NULL".
    /daemons/ipa-kdb/ipa_kdb_mspac.c:2077: null: At condition
    "client_entry", the value of "client_entry" must be "NULL".
    /daemons/ipa-kdb/ipa_kdb_mspac.c:2077: dead_error_condition: The condition
    "client_entry" cannot be true.
    /daemons/ipa-kdb/ipa_kdb_mspac.c:2077:
    dead_error_line: Execution cannot reach the expression "client_entry" inside
    this statement: "kerr = ipadb_get_pac(contex...".
    """
    
    This is a part of a series of patches related to
    https://fedorahosted.org/freeipa/ticket/4795
    
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>