allow for arbitrary kwargs in image client

in order to upload 3 part images with our glance client you need
to allow for passing arbitrary metadata to the image (ramdisk_id
and kernel_id). Remove our kwargs filter to let that happen.

Prereq of blueprint:javelin2

Change-Id: Idff078a2a225a6531b6ce0cf49cb03cc75618e32
Merge "allow for arbitrary kwargs in image client"