ci: add cleanup step, also timeout and timestamps

Signed-off-by: Jakub Sokołowski <jakub@status.im>

ci/Jenkinsfile

@@ -7,6 +7,8 @@ pipeline {
   }
 
   options {
+    timestamps()
+    timeout(time: 5, unit: 'MINUTES')
     disableConcurrentBuilds()
     buildDiscarder(logRotator(
       numToKeepStr: '20',
@@ -35,4 +37,8 @@ pipeline {
       }
     }
   }
+
+  post {
+    cleanup { cleanWs() }
+  }
 }