Add a hidden combine-logs flag (#4766)
Add a hidden combine-logs flag (#4766)

This can be used when errors are happening early on to avoid them being
swallowed by logGate.

This also does a bit of cleanup of format env var checking --
helper/logging internally looks for this so it was totally unnecessary
since moving to hclog.
hashicorp/vault,rnaveiras/vault,hartsock/vault,joelthompson/vault,kingland/vault,hartsock/vault,rnaveiras/vault,kingland/vault,kingland/vault,hartsock/vault,hashicorp/vault,kingland/vault,kingland/vault,hashicorp/vault,joelthompson/vault,hashicorp/vault,rnaveiras/vault,quixoten/vault,joelthompson/vault,hashicorp/vault,quixoten/vault,hartsock/vault,joelthompson/vault,quixoten/vault,rnaveiras/vault,rnaveiras/vault,hashicorp/vault,quixoten/vault,hartsock/vault