handle errors in client calls

[v0idpwn]

brod_client safe_gen_call implementation leaked timeouts

Closes #468

[zmstone]

thanks for the PR.
but the reason reported in #468 isn't {timeout, _} rather

[
  {{'localhost', 29092},
   {{{:kpro_req, #Reference<0.3351001794.2516844547.112162>, :api_versions, 0,
      false, []}, :timeout},
    [
      {:kpro_lib, :send_and_recv_raw, 4, [file: 'src/kpro_lib.erl', line: 70]},
      {:kpro_lib, :send_and_recv, 5, [file: 'src/kpro_lib.erl', line: 81]},
      {:kpro_connection, :query_api_versions, 4,
       [file: 'src/kpro_connection.erl', line: 246]},
      {:kpro_connection, :init_connection, 2,
       [file: 'src/kpro_connection.erl', line: 233]},
      {:kpro_connection, :init, 4, [file: 'src/kpro_connection.erl', line: 170]},
      {:proc_lib, :init_p_do_apply, 3, [file: 'proc_lib.erl', line: 226]}
    ]}}
]

which is the {error, Errors} where Errors is a list of per-host error, returned from kpro_brokers:connect_any https://github.com/kafka4beam/kafka_protocol/blob/9ee00f2efa97df23c13d12a48196bed11e183f41/src/kpro_brokers.erl#L294
which in turn caused this exit exception:

brod/src/brod_client.erl

Line 554 in f88130e

{error, Reason} -> erlang:exit(Reason)

[v0idpwn]

Oh, I see! Thats a call with infinity timeout.

[v0idpwn]

Pushed a fix for that

[zmstone]

Suggested change

	exit : {reason, _} ->
	{error, reason}
	exit : Reason ->
	{error, {client_down, Reason}}

[zmstone]

please help to update changelog.md (bump to 3.16.2)

[zmstone]

#492