Downgrade Exclusive Lease warnings from Geo Log Cursor to debug

These warnings happen every 30 seconds, generating a lot of noise.

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/6428

ee/changelogs/unreleased/tc-geo-log-cursor-suppress-lease-errors.yml

+---
+title: 'Geo: Downgrade Exclusive Lease warnings from Log Cursor to debug'
+merge_request: 7476
+author:
+type: changed

ee/lib/gitlab/geo/log_cursor/lease.rb

@@ -23,7 +23,7 @@ module Gitlab
 
           unless lease[:ttl].zero? || exclusive_lease.same_uuid?
             $stdout.puts lease_taken_message
-            logger.info(lease_taken_message)
+            logger.debug(lease_taken_message)
 
             return lease
           end

ee/spec/lib/gitlab/geo/log_cursor/lease_spec.rb

@@ -41,6 +41,22 @@ describe Gitlab::Geo::LogCursor::Lease, :clean_gitlab_redis_shared_state do
       expect(result[:uuid]).to be_present
     end
 
+    it 'does not log an error or info message when could not obtain lease' do
+      logger = spy(:logger)
+      lease = stub_exclusive_lease(described_class::LEASE_KEY, 'uuid')
+
+      allow(lease).to receive(:try_obtain_with_ttl).and_return({ ttl: 10, uuid: 'uuid' })
+      allow(lease).to receive(:same_uuid?).and_return(false)
+      allow(described_class).to receive(:exclusive_lease).and_return(lease)
+      allow(described_class).to receive(:logger).and_return(logger).at_least(:once)
+
+      expect(logger).not_to receive(:info)
+      expect(logger).not_to receive(:error)
+      expect(logger).to receive(:debug).with('Cannot obtain an exclusive lease. There must be another process already in execution.')
+
+      described_class.try_obtain_with_ttl {}
+    end
+
     it 'returns > 0 if there is a lease' do
       allow(described_class).to receive(:try_obtain_with_ttl).and_return({ ttl: 1, uuid: false })