kdump-lib: fix prepare_cmdline
    
    Resolves: bz2169720
    Upstream: src.fedoraproject.org/rpms/kexec-tools.git
    Conflicts: drop removal of irqpoll in prepare_cmdline due to missing
               d55a056 ("kdumpctl: move aws workaround to kdump-lib") and
               d593bfa ("KDUMP_COMMANDLINE: remove irqpoll parameter on aws aarch64 platform")
    
    commit 0f6ad91be85d5aec983a00ca54adb1b130889bc2
    Author: Philipp Rudo <prudo@redhat.com>
    Date:   Thu Jan 12 16:31:07 2023 +0100
    
        kdump-lib: fix prepare_cmdline
    
        A recently added unit test found that prepare_cmdline has several
        problems. For example an empty remove list will remove all spaces or
        when the cmdline contains a parameter with quoted values containing
        spaces will only remove the beginning up to the first space. Furthermore
        the old design requires lots of subshells and pipes.
    
        This patch rewrites prepare_cmdline in a way that makes the unit test
        happy and tries to use as many bash built-ins as possible.
    
        Signed-off-by: Philipp Rudo <prudo@redhat.com>
        Reviewed-by: Coiby Xu <coxu@redhat.com>
    
    Signed-off-by: Philipp Rudo <prudo@redhat.com>
    Signed-off-by: Tao Liu <ltao@redhat.com>