make host/bucket-determination more robust
make host/bucket-determination more robust

Change-Id: I45b908f3c0ae3014445d89a79723b511b3b2324d

pjxiao/yum-s3-plugin,jbraeuer/yum-s3-plugin,pjxiao/yum-s3-plugin,jbraeuer/yum-s3-plugin