Fix ci_stage_1.groovy to take ROBOT_TAG_NAME as a string

This change will read the param ROBOT_TAG_NAME and add it as a string
param to be passed to downstream jobs, instead of a boolean param, as
it was wrongly doing.

Change-Id: I3b7042dc41cd9a270386c91fdbaa7987e23af655
Signed-off-by: garciadeblas <gerardo.garciadeblas@telefonica.com>
diff --git a/jenkins/ci-pipelines/ci_stage_1.groovy b/jenkins/ci-pipelines/ci_stage_1.groovy
index 306b9fd..a4aca75 100644
--- a/jenkins/ci-pipelines/ci_stage_1.groovy
+++ b/jenkins/ci-pipelines/ci_stage_1.groovy
@@ -76,7 +76,7 @@
         }
         if ( params.ROBOT_TAG_NAME )
         {
-            downstream_params.add(booleanParam(name: 'ROBOT_TAG_NAME', value: params.ROBOT_TAG_NAME))
+            downstream_params.add(string(name: 'ROBOT_TAG_NAME', value: params.ROBOT_TAG_NAME))
         }
 
         if ( params.STAGE )