ipatests: Adding --no-dnssec-validation option for healthcheck
    
    healthcheck related tests are failing because of the below issue
    "client @0x7f8ee47c4d48 : servfail cache hit (CD=0)"
    and as a result healthcheck related packages are not downloaded on test
    system.
    Hence adding the --no-dnssec-validation option to install_master
    and install_replica function
    
    https://pagure.io/freeipa/issue/9151
    
    Signed-off-by: Sudhir Menon <sumenon@redhat.com>
    Reviewed-By: Florence Blanc-Renaud <frenaud@redhat.com>
    Reviewed-By: Anuja More <amore@redhat.com>
    Reviewed-By: Michal Polovka <mpolovka@redhat.com>
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>