nbd/client: fix nbd_negotiate_simple_meta_context

nbd/client: fix nbd_negotiate_simple_meta_context

Initialize received variable. Otherwise, is is possible for server to
answer without any contexts, but we will set context_id to something
random (received_id is not initialized too) and return 1, which is
wrong.

To solve it, just initialize received to false. Initialize received_id
too, just to make all possible checkers happy.

Bug was introduced in 78a33ab58782efdb206de14 "nbd: BLOCK_STATUS for
standard get_block_status function: client part" with the whole
function.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20180427142002.21930-2-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
CC: qemu-stable@nongnu.org
Signed-off-by: Eric Blake <eblake@redhat.com>
(cherry picked from commit 89aa0d87634e2cb98517509dc8bdb876f26ecf8b)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>