Fix duplicated etag generation

bmcweb generates the duplicated etags on GET and it may cause the
PATCH failure if etag is used - e.g. redfishtool..

This commit is to put only one Etag on http_response on GET.

Tested:

- Check the duplicated Etag on GET, and check it after fix

Before:
```
$ curl -v -k -X GET https://admin:${password}@${bmc}:18080/redfish/v1/AccountService/Accounts/readonly
...
< ETag: "D4B30BB4"
< ETag: "D4B30BB4"
```

After:
```
$ curl -v -k -X GET https://admin:${password}@${bmc}:18080/redfish/v1/AccountService/Accounts/readonly
...
< ETag: "D4B30BB4"
```

Change-Id: I5361919c5671b546181a26de792bc57de2c4f670
Signed-off-by: Myung Bae <myungbae@us.ibm.com>

0 files changed, 0 insertions, 0 deletions