qemu: command: escape smbios entry strings
qemu: command: escape smbios entry strings

We pass free-form strings from the users to qemu, thus we need escape
commas since they are passed to qemu monitor.

Partially resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1373535

eskultety/libvirt,fabianfreyer/libvirt,nertpinx/libvirt,fabianfreyer/libvirt,datto/libvirt,nertpinx/libvirt,jardasgit/libvirt,datto/libvirt,andreabolognani/libvirt,datto/libvirt,andreabolognani/libvirt,datto/libvirt,VenkatDatta/libvirt,jfehlig/libvirt,andreabolognani/libvirt,jfehlig/libvirt,andreabolognani/libvirt,olafhering/libvirt,VenkatDatta/libvirt,olafhering/libvirt,nertpinx/libvirt,jfehlig/libvirt,eskultety/libvirt,jfehlig/libvirt,olafhering/libvirt,jardasgit/libvirt,andreabolognani/libvirt,taget/libvirt,taget/libvirt,fabianfreyer/libvirt,zippy2/libvirt,taget/libvirt,libvirt/libvirt,crobinso/libvirt,zippy2/libvirt,eskultety/libvirt,zippy2/libvirt,crobinso/libvirt,VenkatDatta/libvirt,libvirt/libvirt,jardasgit/libvirt,eskultety/libvirt,libvirt/libvirt,nertpinx/libvirt,taget/libvirt,taget/libvirt,VenkatDatta/libvirt,crobinso/libvirt,zippy2/libvirt,crobinso/libvirt,fabianfreyer/libvirt,eskultety/libvirt,olafhering/libvirt,VenkatDatta/libvirt,nertpinx/libvirt,jardasgit/libvirt,datto/libvirt,jardasgit/libvirt,fabianfreyer/libvirt,libvirt/libvirt