Function Update if config/secret changes (#1224)

* Config and secret change to invoke function update
* Added recycle function for pool manager as well - where it recycles the specialized pods
* Switched to rolling update of pods and env variable based change instead of deleting pods in new deploy executor

pkg/apis/fission.io/v1/const.go

@@ -21,6 +21,11 @@ const (
 	POOLMGR_INSTANCEID_LABEL  string = "poolmgrInstanceId"
 )
 
+const (
+	//LastUpdateTimestamp env variable is used for updating configmaps and secrets in pods
+	LastUpdateTimestamp string = "LASTUPDATE_TIMESTAMP"
+)
+
 const (
 	ChecksumTypeSHA256 ChecksumType = "sha256"
 )