* client: accommodate Consul 1.14.0 gRPC and agent self changes.
Consul 1.14.0 changed the way in which gRPC listeners are
configured, particularly when using TLS. Prior to the change, a
single listener was responsible for handling plain-text and
encrypted gRPC requests. In 1.14.0 and beyond, separate listeners
will be used for each, defaulting to 8502 and 8503 for plain-text
and TLS respectively.
The change means that Nomad’s Consul Connect integration would not
work when integrated with Consul clusters using TLS and running
1.14.0 or greater.
The Nomad Consul fingerprinter identifies the gRPC port Consul has
exposed using the "DebugConfig.GRPCPort" value from Consul’s
“/v1/agent/self” endpoint. In Consul 1.14.0 and greater, this only
represents the plain-text gRPC port which is likely to be disbaled
in clusters running TLS. In order to fix this issue, Nomad now
takes into account the Consul version and configured scheme to
optionally use “DebugConfig.GRPCTLSPort” value from Consul’s agent
self return.
The “consul_grcp_socket” allocrunner hook has also been updated so
that the fingerprinted gRPC port attribute is passed in. This
provides a better fallback method, when the operator does not
configure the “consul.grpc_address” option.
* docs: modify Consul Connect entries to detail 1.14.0 changes.
* changelog: add entry for #15309
* fixup: tidy tests and clean version match from review feedback.
* fixup: use strings tolower func.
