Make "Missing endpoint..." error display ServiceCatalog

This is a follow-up to #177. That one added the display of the `criteria`. This one makes it also display the `ServiceCatalog` so you can see why things didn't match.

This makes it easier to debug why we failed to get a URL.

Output looks like this:

```
❯ go run marca/test_gophercloud.go
panic: Missing endpoint, or insufficient privileges to access endpoint; criteria = gophercloud.ApiCriteria{Name:"nova", Type:"", Region:"RegionOne", VersionId:"", UrlChoice:0, IgnoreEnvVars:false}; serviceCatalog = []gophercloud.CatalogEntry{
    {
        Name:      "Volume Service",
        Type:      "volume",
        Endpoints: {
            {Region:"RegionOne", TenantId:"", PublicURL:"http://api-foo.client.metacloud.net:8776/v1/a5920c8f7bf6441a9e2e96eb7b62d1d5", InternalURL:"http://api.foo.pv.metacloud.in:8776/v1/a5920c8f7bf6441a9e2e96eb7b62d1d5", VersionId:"", VersionInfo:"", VersionList:""},
        },
    },
    {
        Name:      "Image Service",
        Type:      "image",
        Endpoints: {
            {Region:"RegionOne", TenantId:"", PublicURL:"http://api-foo.client.metacloud.net:9292/v1", InternalURL:"http://api.foo.pv.metacloud.in:9292/v1", VersionId:"", VersionInfo:"", VersionList:""},
        },
    },
    {
        Name:      "Compute Service",
        Type:      "compute",
        Endpoints: {
            {Region:"RegionOne", TenantId:"", PublicURL:"http://api-foo.client.metacloud.net:8774/v2/a5920c8f7bf6441a9e2e96eb7b62d1d5", InternalURL:"http://api.foo.pv.metacloud.in:8774/v2/a5920c8f7bf6441a9e2e96eb7b62d1d5", VersionId:"", VersionInfo:"", VersionList:""},
        },
    },
    {
        Name:      "EC2 Service",
        Type:      "ec2",
        Endpoints: {
            {Region:"RegionOne", TenantId:"", PublicURL:"http://api-foo.client.metacloud.net:8773/services/Cloud", InternalURL:"http://api.foo.pv.metacloud.in:8773/services/Cloud", VersionId:"", VersionInfo:"", VersionList:""},
        },
    },
    {
        Name:      "Identity Service",
        Type:      "identity",
        Endpoints: {
            {Region:"RegionOne", TenantId:"", PublicURL:"http://api-foo.client.metacloud.net:5000/v2.0", InternalURL:"http://api.foo.pv.metacloud.in:5000/v2.0", VersionId:"", VersionInfo:"", VersionList:""},
        },
    },
}
```