Bug # 1166307 - Updated Nicira NVP Plugin Paths

Replaced all instances of 'nicira_nvp_plugin' in module and
configuration paths with ''. That is to say instances of
quantum.plugins.nicira.nicira_nvp_plugin became quantum.plugins.nicira.
Instances of quantum/plugins/nicira/nicira_nvp_plugin became
quantum/plugins/nicira. Instances where it appears the update has
already been made have been left as is.

Change-Id: I272ae1f01a7654ec37b1051c8169eb0ef60aa987
Merge "Bug # 1166307 - Updated Nicira NVP Plugin Paths"