request: remove unnecessary check
request: remove unnecessary check

headers['ETag'] becomes empty only when headers['Content-MD5'] is also empty,
but the check is already done.

Change-Id: I7a3886fd5d45f5fd03ba311377b57b3770ed764a

tumf/swift3,KoreaCloudObjectStorage/swift3,KoreaCloudObjectStorage/swift3,stackforge/swift3,stackforge/swift3,swiftstack/swift3-stackforge,swiftstack/swift3-stackforge,tumf/swift3