rgw: set default region as master

A default region that is automaticall created needs to be
set as the master.

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>
test: update cli test

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>
rgw: add 'delete' to signed subresources list

This fixes a regression that removed 'delete' from the signed
subresources list, thus made it impossible to authenticate
certain multipart object operations.

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>