UploadPack: Test filtering by AdvertiseRefsHook in stateless transports

UploadPack: Test filtering by AdvertiseRefsHook in stateless transports

AdvertiseRefsHook is used to limit the visibility of the refs in Gerrit.
If this hook is not called, then all refs are treated as visible,
causing the server to serve commits reachable from branches the client
should not be able to access, if asked to via a request naming a guessed
object id.

Until 3a529361a76e8267467071e0b13ebb36b97d8fb2 (Call AdvertiseRefsHook
before validating wants, 2018-12-18), UploadPack would invoke this hook
at ref advertisement time but not during negotiation and when serving a
pack file.  Add a test to avoid regressing. Stateful bidirectional
transports were not affected, so the test uses HTTP.

[jn: split out when backporting the fix to stable-4.5.  The test passes
 as long as v4.9.0.201710071750-r~169 (fetch: Accept any SHA-1 on lhs of
 refspec, 2017-06-04) is cherry picked along with it.]

Change-Id: I8c017107336adc7cb4c826985779676bf043e648
Signed-off-by: Masaya Suzuki <masayasuzuki@google.com>
Signed-off-by: Jonathan Nieder <jrn@google.com>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>