PLT-6090 adding ability to read license file from disk (#5895)

* PLT-6090 adding ability to read license file from disk

* Fixing unit test that fails only sometimes

* Fixing test that fails randomly

api/license.go

@@ -68,6 +68,8 @@ func addLicense(c *Context, w http.ResponseWriter, r *http.Request) {
 		c.Err = err
 		return
 	} else {
+		app.ReloadConfig()
+		app.InvalidateAllCaches()
 		c.LogAudit("success")
 		w.Write([]byte(license.ToJson()))
 	}