clone: remove fetch_if_missing=0

clone: remove fetch_if_missing=0

Commit 6462d5eb9a ("fetch: remove fetch_if_missing=0", 2019-11-08)
strove to remove the need for fetch_if_missing=0 from the fetching
mechanism, so it is plausible to attempt removing fetch_if_missing=0
from clone as well. But doing so reveals a bug - when the server does
not send an object directly pointed to by a ref, this should be an
error, not a trigger for a lazy fetch. (This case in the fetching
mechanism was covered by a test using "git clone", not "git fetch",
which is why the aforementioned commit didn't uncover the bug.)

The bug can be fixed by suppressing lazy-fetching during the
connectivity check. Fix this bug, and remove fetch_if_missing from
clone.

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>