Add test for silence deletion
Add test for silence deletion

brunoqc/alertmanager,brancz/alertmanager,tinytub/alertmanager,Kellel/alertmanager,prometheus/alertmanager,brancz/alertmanager,Kellel/alertmanager,tinytub/alertmanager,tyrken/alertmanager,GoogleCloudPlatform/alertmanager,brunoqc/alertmanager,pdf/alertmanager,novilabs/alertmanager,Aloomaio/alertmanager,novilabs/alertmanager,Aloomaio/alertmanager,brancz/alertmanager,brunoqc/alertmanager,pdf/alertmanager,tyrken/alertmanager,tyrken/alertmanager,MonsantoCo/alertmanager,brunoqc/alertmanager,joehandzik/alertmanager,MonsantoCo/alertmanager,tbouvet/alertmanager,MonsantoCo/alertmanager,joehandzik/alertmanager,pdf/alertmanager,ericgerling/alertmanager,novilabs/alertmanager,prometheus/alertmanager,Kellel/alertmanager,novilabs/alertmanager,MonsantoCo/alertmanager,sarathsp06/alertmanager,ericgerling/alertmanager,prometheus/alertmanager,pdf/alertmanager,tbouvet/alertmanager,brancz/alertmanager,Aloomaio/alertmanager,GoogleCloudPlatform/alertmanager,GoogleCloudPlatform/alertmanager,joehandzik/alertmanager,GoogleCloudPlatform/alertmanager,tbouvet/alertmanager,prometheus/alertmanager,sarathsp06/alertmanager,ericgerling/alertmanager,tinytub/alertmanager,tyrken/alertmanager,sarathsp06/alertmanager