CAN NOT access ceph object storage via swift

I setup a ceph object storage and enable swift access. try to access ceph via swift, successed:

```bash
# swift -A http://10.125.224.26:7480/auth/v1.0 -U tstack:swift -K tstackqwer666 list
regswfit
test
```

then, i want use chartmuseum to access ceph object storage via swift:

```bash
export OS_AUTH_URL=http://10.125.224.26:7480/auth/v1.0
export OS_USERNAME=tstack:swift
export OS_PASSWORD=tstackqwer666
export STORAGE: openstack
export STORAGE_OPENSTACK_CONTAINER=regswfit
export STORAGE_OPENSTACK_REGION=openstack

./chartmuseum
```

then error happened:

```
panic: Openstack (authenticate): Authentication failed

goroutine 1 [running]:
github.com/helm/chartmuseum/vendor/github.com/kubernetes-helm/chartmuseum/pkg/storage.NewOpenstackOSBackend(0xc00003613c, 0x8, 0x0, 0x0, 0xc0000360a9, 0x9, 0x0, 0x0, 0x0)
/home/xinjiexu/workspace/dev_projs/tcnp/gopath/src/github.com/helm/chartmuseum/vendor/github.com/kubernetes-helm/chartmuseum/pkg/storage/openstack.go:94 +0xcc7
main.openstackBackendFromConfig(0xc0002202c0, 0x0, 0x0)
/home/xinjiexu/workspace/dev_projs/tcnp/gopath/src/github.com/helm/chartmuseum/cmd/chartmuseum/main.go:158 +0x218
main.backendFromConfig(0xc0002202c0, 0x0, 0x0)
/home/xinjiexu/workspace/dev_projs/tcnp/gopath/src/github.com/helm/chartmuseum/cmd/chartmuseum/main.go:100 +0x9a2
main.cliHandler(0xc000272dc0)
/home/xinjiexu/workspace/dev_projs/tcnp/gopath/src/github.com/helm/chartmuseum/cmd/chartmuseum/main.go:46 +0x15e
github.com/helm/chartmuseum/vendor/github.com/urfave/cli.HandleAction(0x12597e0, 0x14a5868, 0xc000272dc0, 0x0, 0x0)
/home/xinjiexu/workspace/dev_projs/tcnp/gopath/src/github.com/helm/chartmuseum/vendor/github.com/urfave/cli/app.go:492 +0x1cc
github.com/helm/chartmuseum/vendor/github.com/urfave/cli.(*App).Run(0xc000319380, 0xc0000301b0, 0x1, 0x1, 0x0, 0x0)
/home/xinjiexu/workspace/dev_projs/tcnp/gopath/src/github.com/helm/chartmuseum/vendor/github.com/urfave/cli/app.go:264 +0xa53
main.main()
/home/xinjiexu/workspace/dev_projs/tcnp/gopath/src/github.com/helm/chartmuseum/cmd/chartmuseum/main.go:36 +0x2a5
```

chartmuseum version: 0.7.1
ceph version: 12.2.4 (52085d5249a80c5f5121a76d6288429f35e4e77b) luminous (stable)