daemons: Tweak read sizes
daemons: Tweak read sizes

Make sure we never read more than one page unless requested on the first
read. This helps for e.g. sniffing and gstreamer (which reads in 4k blocks
with seeks inbetween).

Also, further limit the max size request, because 512k seems very ridicoulus.

gicmo/gvfs,halfline/gvfs,gicmo/gvfs,gicmo/gvfs,xkahn/gvfs-cmis,xkahn/gvfs-cmis,halfline/gvfs,xkahn/gvfs-cmis,gicmo/gvfs,xkahn/gvfs-cmis,halfline/gvfs