Handle GET on zero content length failure case.

Added a fake_file class that implements minimal set of functions that
are invoked by the code in GET.

BUG: 987841

https://bugzilla.redhat.com/show_bug.cgi?id=987841

Change-Id: I5bdf5be1c0c4c8231f34c9be529e6edc83774f2e
Signed-off-by: Chetan Risbud <crisbud@redhat.com>
Reviewed-on: http://review.gluster.org/5511
Reviewed-by: Luis Pabon <lpabon@redhat.com>
Tested-by: Luis Pabon <lpabon@redhat.com>