Each implementation keeps its provider client in an interface{} field that
Setup assigns, so an unconfigured store holds nil - and asserting nil to
the provider's client type panics:
panic: interface conversion: interface {} is nil, not *oss.Client
The upload endpoint reaches that path for any request naming a provider
the deployment never configured.
Three more things were wrong in the same files. OXS.Setup printed a
failure and returned the store anyway, handing back exactly the broken
object that panics. HuaWeiOBS.UpLoad printed the provider's error and
returned nil, so a failed upload reported success. Both it and
QiNiuKODO.UpLoad asserted the local path was a string without checking.
The tests asked the reader to paste their own credentials, so they failed
for everyone who did not. They now cover the guards and skip the part
that needs a provider unless credentials are in the environment.
