ipatests: Add healthcheck test for FileSystemSpaceCheck
    
    Create a large file in one of the checked filesystems beyond
    the allowed threshold and ensure that both the minimum space
    and minimum percent errors are reported.
    
    Signed-off-by: Rob Crittenden <rcritten@redhat.com>
    Reviewed-By: Mohammad Rizwan <myusuf@redhat.com>
    Reviewed-By: Florence Blanc-Renaud <flo@redhat.com>