Use HTTPRequest instead of HTTPRequestV3 for v2/v2.1 tests

This patch replace HTTPRequestV3 with HTTPRequest for
test_shelve unit test case, which can be shared between
v2 and v21

Partially implements blueprint v2-on-v3-api
Change-Id: I732335e1f4885a067e42c48c75417ba0b4aba192
Merge "Use HTTPRequest instead of HTTPRequestV3 for v2/v2.1 tests"