Stop environments from needless refreshes

Currently, Environment has the following ReactiveCache setting:

- reactive_cache_refresh_interval = 1.minute (Default Value)
- reactive_cache_lifetime = 10.minutes (Default Value)

This causes ReactiveCacheWorker to run at least 10 times before the
lifetime of the `:active` key expires.

When ReactiveCache receives a request for a currently `:active`
request, the active request is expires time is reset to
`reactive_cache_lifetime` from the current time - meaning that the
redis keys will always stay active while they are being requested.

Changing the values to:

- reactive_cache_refresh_interval = 1.minute
- reactive_cache_lifetime = 55.seconds

will cause the lifetime of the `:active` key to expire sooner than the
ReactiveCacheWorker runs only if the value key has not been requested
in the interim. If the user has navigated away from the page, the
ReactiveCacheWorker will NOT continue to refresh the data for 10
minutes.  The next execution of the ReactiveCacheWorker will be the
last one.

I left the refresh interval at 1.minute since our users probably
expect to get refreshes on 1 minute intervals.

app/models/environment.rb

@@ -4,6 +4,9 @@ class Environment < ApplicationRecord
   include Gitlab::Utils::StrongMemoize
   include ReactiveCaching
 
+  self.reactive_cache_refresh_interval = 1.minute
+  self.reactive_cache_lifetime = 55.seconds
+
   belongs_to :project, required: true
 
   has_many :deployments, -> { visible }, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent

spec/models/environment_spec.rb

@@ -744,6 +744,12 @@ describe Environment, :use_clean_rails_memory_store_caching do
       allow(environment).to receive(:deployment_platform).and_return(double)
     end
 
+    context 'reactive cache configuration' do
+      it 'does not continue to spawn jobs' do
+        expect(described_class.reactive_cache_lifetime).to be < described_class.reactive_cache_refresh_interval
+      end
+    end
+
     context 'reactive cache is empty' do
       before do
         stub_reactive_cache(environment, nil)