Update stubdom memory allocation to 44MB
Update stubdom memory allocation to 44MB

Since 677a79b "hvm: change default graphics to std vga ('xen')",
stubdomain uses 44MB RAM

QubesOS/qubes-issues#1136

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