Remove objectify decorator from dbapi's {get, register}_conductor()

This patch removes the objectify decorator from the get_conductor and
register_conductor dbapi's methods.

For get_condutor() method there's an objects interface to it so this patch
make the code/tests use the object interface vs direct calls to dbapi.

The problem with the objectify decorator is that dbapi methods
doesn't get the context, so when forming the RPC object using the
decorator we can't store the context within the object (which is what
we want to do to have consistent object interfaces).

Partial-Bug: 1314732
Change-Id: I1a955a59435b35277f3bbff2c02c07dd1a4c1d66
Merge "Remove objectify decorator from dbapi's {get, register}_conductor()"