UploadPack: consume delimiter in object-info command

UploadPack: consume delimiter in object-info command

The 'size' packet line is an argument, so it
must be preceeded by a 0001 delimiter. See also git's
t5701-git-serve.sh test,

https://github.com/git/git/blob/8b8d9a2/t/t5701-git-serve.sh#L329

Without this fix, the server will choke on the delimiter line, saying
PackProtocolException: unexpected <empty string>

To test, I ran Gerrit locally with this fix

$ curl -X POST   -H 'git-protocol: version=2'   -H 'content-type:
application/x-git-upload-pack-request'   -H 'accept:
application/x-git-upload-pack-result'   --data
$'0018command=object-info\n00010009size\n0031oid
d38b1b92bdb2893eb4505667375563f2d6d4086b\n0000'
http://localhost:8080/git.git/git-upload-pack

=>

0008size0032d38b1b92bdb2893eb4505667375563f2d6d4086b 268590000

The same command completes identically on Gitlab (which supports the
object-info command)

$ curl -X POST   -H 'git-protocol: version=2'   -H 'content-type:
application/x-git-upload-pack-request'   -H 'accept:
application/x-git-upload-pack-result'   --data
$'0018command=object-info\n00010009size\n0031oid
d38b1b92bdb2893eb4505667375563f2d6d4086b\n0000'
https://gitlab.com/gitlab-org/git.git/git-upload-pack

=>

0008size0032d38b1b92bdb2893eb4505667375563f2d6d4086b 268590000

In this case, the blob is for the COPYING file in the Git source tree,
which is 26859 bytes long.

Change-Id: Ief4ce1eb9303a3b2479547d7950ef01c7c28f472