Fixes, failback procedure and notes in README.md

2 jobs for database_wrangler_master in 13 seconds
Status Job ID Name Coverage
  Test
failed #2723818
references

00:00:10

passed #2723817
shellcheck

00:00:13

 
Name Stage Failure
failed
references Test
+ [[ -x /builds/gitlab-com/migration/bin/scripts/02_failover/060_go/p04/073-check-pgbouncer-node-in-gcp.sh ]]
+ IFS=
+ read -r file
+ [[ -f /builds/gitlab-com/migration/bin/scripts/02_failover/060_go/p04/074-convert-azure-master-to-gcp-standby.sh ]]
+ echo 'bin/scripts/02_failover/060_go/p04/074-convert-azure-master-to-gcp-standby.sh is missing or not executable'
bin/scripts/02_failover/060_go/p04/074-convert-azure-master-to-gcp-standby.sh is missing or not executable
+ grep -En bin/scripts/02_failover/060_go/p04/074-convert-azure-master-to-gcp-standby.sh '/builds/gitlab-com/migration/.gitlab/issue_templates/*.md'
grep: /builds/gitlab-com/migration/.gitlab/issue_templates/*.md: No such file or directory
ERROR: Job failed: exit code 2