Remove LOG outputs from v2.1 API layer

There are some debug/audit log messages about normal API operations
in each API method, but Nova WSGI framework has already output the
similar messages. So these messages are meaningless, and this patch
removes them.
This patch removes LOG outputs of InterfaceAttachFailed cases also,
because they are already output on driver layer(vmwareapi, libvirt)
and duplicated now.

Partially implements blueprint v2-on-v3-api

Change-Id: Ib645d1c320e6104bad34c2d7238db399e8d1ea42
Merge "Remove LOG outputs from v2.1 API layer"