Disable load balancing if running in rake task

rails now can run rake tasks, so we can't rely on the executable name

ee/lib/gitlab/database/load_balancing.rb

@@ -84,7 +84,7 @@ module Gitlab
 
       # Returns true if load balancing is to be enabled.
       def self.enable?
-        return false if program_name == 'rake' || Gitlab::Runtime.sidekiq?
+        return false if Gitlab::Runtime.rake? || Gitlab::Runtime.sidekiq?
         return false unless self.configured?
 
         true

ee/spec/lib/gitlab/database/load_balancing_spec.rb

@@ -146,7 +146,7 @@ RSpec.describe Gitlab::Database::LoadBalancing do
     end
 
     it 'returns false when running inside a Rake task' do
-      expect(described_class).to receive(:program_name).and_return('rake')
+      allow(Gitlab::Runtime).to receive(:rake?).and_return(true)
 
       expect(described_class.enable?).to eq(false)
     end