Calendar sensor with Schedule: @every 30s triggers only once

[DmitryBe]

Describe the bug
Calendar sensor with Schedule: @every 30s triggers only once

To Reproduce
create sensor with following config:

apiVersion: argoproj.io/v1alpha1
kind: Sensor
metadata:
name: inline-example
namespace: playground
labels:
sensors.argoproj.io/controller-instanceid: axis
spec:
signals:
- name: time
calendar:
schedule: "@every 30s"
triggers:
- name: inline-workflow-trigger
resource:
namespace: playground
group: argoproj.io
version: v1alpha1
kind: Workflow
source:
inline: |
apiVersion: argoproj.io/v1alpha1
kind: Workflow
metadata:
generateName: job-hello-world-
spec:
entrypoint: whalesay
templates:
-
container:
args:
- "hello world"
command:
- cowsay
image: "docker/whalesay:latest"
name: whalesay

specifying schedule: "@every 30s" i expect it to repeat every 30 seconds;
sensor triggers once and transitions to Phase: Complete

[VaibhavPage]

This issue is being addressed in #92