dispvm: do not limit DispVM memory to reported allocated size
dispvm: do not limit DispVM memory to reported allocated size

Apparently it doesn't work with some kernels - saved domain still needs
original memory amount to restore successfully. This happens at least on
3.12.14 kernel.
Because qfile-daemon-dvm always requests 400MB from qmemman, this change
should harm anyone - in any case DispVM needs 400MB free memory to
start.

Note that "xl mem-set" line is still there, which makes savefile somehow
smaller (so faster restore).

QubesOS/qubes-core-admin,woju/qubes-core-admin,woju/qubes-core-admin,QubesOS/qubes-core-admin,marmarek/qubes-core-admin,woju/qubes-core-admin,QubesOS/qubes-core-admin,marmarek/qubes-core-admin,woju/qubes-core-admin,marmarek/qubes-core-admin