kdumpctl: use kdump_get_conf_val to read config values
    
    upstream: fedora
    resolves: bz2003832
    conflict: none
    
    commit 01613b7211a3de096a889000817ebb9da513f4af
    Author: Kairui Song <kasong@redhat.com>
    Date:   Tue Aug 3 22:50:02 2021 +0800
    
        kdumpctl: use kdump_get_conf_val to read config values
    
        Also fixed kdumpctl, use `awk` instead of `cut` to read
        core_collector's executable name correctly when its arguments
        are not seperated by space.
    
        Signed-off-by: Kairui Song <kasong@redhat.com>
        Acked-by: Philipp Rudo <prudo@redhat.com>
    
    Signed-off-by: Tao Liu <ltao@redhat.com>