Ticket 49204 - Fix lower bounds on import autosize + On small VM, autotune breaks the access of the suffixes
    
    Bug Description:
        ldif2db in some cases may set a cache of 0, which may y break imports.
    
        Under memory pressure, the amount of available memory at startup
        can be so low that the configured cachememsize will be rejected
        (unwilling to perform).
        This should leave the cachememsize being "0" (default)
        This conduct to be unable to access the suffix pages.
    
    Fix Description:
    
     * autosize set an incorrect percentage which was too high.
     * we did not check the lower bound of the allocation
       so we now set that we must have a minimum allocation.
     * Set entrycache to a minimal value, even if it looks insane
     * add a cap on reduction of caches, so we always allocate a few pages
       at least, and prevent returning 0 to the caller.
    
    https://pagure.io/389-ds-base/issue/49204
    
    Author: wibrown, tbordaz
    
    Review by: tbordaz (Thanks mate, great work with this :) )