Move httpclient to compile scope
Move httpclient to compile scope

Some plugins might require httpclient. For example, AWS SDK uses httpclient.
Forcing it with a test scope would force adding in `cloud-aws` `pom.xml` file the following:

```xml
<dependency>
  <groupId>org.apache.httpcomponents</groupId>
  <artifactId>httpclient</artifactId>
  <scope>compile</scope>
</dependency>
```

It would be better to force in elasticsearch core project the `test` scope.

elastic/elasticsearch-parent,rmuir/elasticsearch-parent,dadoonet/elasticsearch-parent