add HEAD Method support for SSO

Signed-off-by: tobiasKaminsky <tobias@kaminsky.me>

src/main/java/com/nextcloud/android/sso/InputStreamBinder.java

@@ -50,6 +50,7 @@ import org.apache.commons.httpclient.HttpState;
 import org.apache.commons.httpclient.NameValuePair;
 import org.apache.commons.httpclient.methods.DeleteMethod;
 import org.apache.commons.httpclient.methods.GetMethod;
+import org.apache.commons.httpclient.methods.HeadMethod;
 import org.apache.commons.httpclient.methods.InputStreamRequestEntity;
 import org.apache.commons.httpclient.methods.PostMethod;
 import org.apache.commons.httpclient.methods.PutMethod;
@@ -297,6 +298,10 @@ public class InputStreamBinder extends IInputStreamService.Stub {
                 method = new MkColMethod(requestUrl);
                 break;
 
+            case "HEAD":
+                 method = new HeadMethod(requestUrl);
+                 break;
+
             default:
                 throw new UnsupportedOperationException(EXCEPTION_UNSUPPORTED_METHOD);