ec2: allow spaces seperated hostname in metadata

AWS hostname metadata will return space seperated hostname and domain
names when DHCPOptionSet is using multiple domain names. This patch will
cater for this scenario.

datasource/metadata/ec2/metadata.go

@@ -69,7 +69,7 @@ func (ms metadataService) FetchMetadata() ([]byte, error) {
 	}
 
 	if hostname, err := ms.fetchAttribute(fmt.Sprintf("%s/hostname", ms.MetadataUrl())); err == nil {
-		attrs["hostname"] = hostname
+		attrs["hostname"] = strings.Split(hostname, " ")[0]
 	} else if _, ok := err.(pkg.ErrNotFound); !ok {
 		return nil, err
 	}