make findall in novaclient/base.py more efficient

Use /resources instead of /resources/detail to resolve
the resource ID by the name and load the details of the
resource in a separate step. This reduces the overhead
to resolve the resource ID and results in a better runtime
performance.

This patch does not solve the issue that the name resolving
takes place on the client side. For solving this issue new
Nova API methods are necessary.

fixes bug #1202179

Change-Id: Ib753b1d090cb74b2d137c68f6899dad4ae2ec1ca