bs-upload-kernel: Pass limit_packages also on multibuild
    
    Fixes: 0999112774fc ("MyBS: Use buildflags to set which package to build")
    Fixes: 747f601d4156 ("bs-upload-kernel, MyBS, Buildresults: Support multibuild (JSC-SLE#5501, boo#1211226, bsc#1218184)")