Added logging of insufficient local space

When checking for space availability for decompressing the ovf
file in a temporary directory, notify the user and log an error
if there isn't enough space.

Also fixed the return value of space_test_ovf when tarfile raises an
exception and made space_test_ovf a static method.

Change-Id: Id9742144ed5f28399908d2dde116d34d86b3f119
Signed-off-by: Sandro Bonazzola <sbonazzo@redhat.com>