Added a test for empty metadata
Added a test for empty metadata

Here added a test for setting empty object metadata
and checking its value in response headers.

Change-Id: I460302661d150364a95bcd7f0ebbbc2a1e95507a

wenhuizhang/swift,swiftstack/swift,shibaniahegde/OpenStak_swift,tipabu/swift,eatbyte/Swift,aerwin3/swift,tipabu/swift,bouncestorage/swift,thiagodasilva/swift,hbhdytf/mac,tipabu/swift,psachin/swift,larsbutler/swift,dencaval/swift,aerwin3/swift,prashanthpai/swift,dpgoetz/swift,eatbyte/Swift,IPVL/swift-kilo,clayg/swift,Khushbu27/Tutorial,revoer/keystone-8.0.0,openstack/swift,revoer/keystone-8.0.0,matthewoliver/swift,sarvesh-ranjan/swift,hbhdytf/mac2,gold3bear/swift,scality/ScalitySproxydSwift,nadeemsyed/swift,sarvesh-ranjan/swift,hbhdytf/mac,mjwtom/swift,nadeemsyed/swift,iostackproject/IO-Bandwidth-Differentiation,notmyname/swift,nadeemsyed/swift,swiftstack/swift,bradleypj823/swift,smerritt/swift,smerritt/swift,hurricanerix/swift,maginatics/swift,daasbank/swift,hurricanerix/swift,smerritt/swift,hbhdytf/mac2,levythu/swift,AfonsoFGarcia/swift,dpgoetz/swift,rackerlabs/swift,Em-Pan/swift,redbo/swift,NeCTAR-RC/swift,anishnarang/gswift,notmyname/swift,bradleypj823/swift,Khushbu27/Tutorial,hbhdytf/mac2,prashanthpai/swift,matthewoliver/swift,psachin/swift,wenhuizhang/swift,larsbutler/swift,matthewoliver/swift,zackmdavis/swift,scality/ScalitySproxydSwift,clayg/swift,maginatics/swift,openstack/swift,bouncestorage/swift,tipabu/swift,NeCTAR-RC/swift,williamthegrey/swift,dencaval/swift,bkolli/swift,mjzmjz/swift,Seagate/swift,openstack/swift,hurricanerix/swift,takeshineshiro/swift,thiagodasilva/swift,anishnarang/gswift,clayg/swift,gold3bear/swift,mjwtom/swift,rackerlabs/swift,levythu/swift,takeshineshiro/swift,shibaniahegde/OpenStak_swift,AfonsoFGarcia/swift,psachin/swift,williamthegrey/swift,Em-Pan/swift,redhat-openstack/swift,Akanoa/swift,redbo/swift,clayg/swift,redhat-openstack/swift,Seagate/swift,mjzmjz/swift,hbhdytf/mac2,openstack/swift,zackmdavis/swift,psachin/swift,Akanoa/swift,IPVL/swift-kilo,daasbank/swift,smerritt/swift,bkolli/swift,matthewoliver/swift,iostackproject/IO-Bandwidth-Differentiation,notmyname/swift,notmyname/swift,nadeemsyed/swift,hurricanerix/swift,swiftstack/swift