travis: update to go 1.16, and fix selection of ppc64le

[thaJeztah]

let's see if this fixes CI

[thaJeztah]

Ah, interesting;

$ make validate
$ make test
# tests all packages except vendor
go test -v `go list ./... | grep -v /vendor/`
client/command.go:8:2: missing go.sum entry for module providing package golang.org/x/sys/execabs (imported by github.com/docker/docker-credential-helpers/client); to add:
	go get github.com/docker/docker-credential-helpers/client
make: *** [test] Error 1
The command "make test" exited with 2.

[thaJeztah]

no dice; issue with go1.16?

go test -v `go list ./... | grep -v /vendor/`
# github.com/docker/docker-credential-helpers/secretservice.test
/home/travis/.gimme/versions/go1.16.4.linux.amd64/pkg/tool/linux_amd64/link: running gcc failed: exit status 1
/usr/bin/ld: /tmp/go-link-383734037/000006.o: unrecognized relocation (0x2a) in section `.text'
/usr/bin/ld: final link failed: Bad value
collect2: error: ld returned 1 exit status

[thaJeztah]

Hmm updating to focal (ubunu 20.10) of course also requires systemd to be used, which CI doesn't like to be running;

+systemctl start Xvfb.service
==== AUTHENTICATING FOR org.freedesktop.systemd1.manage-units ===
Authentication is required to start 'Xvfb.service'.
Authenticating as: root
Password: Failed to start Xvfb.service: Connection timed out
See system logs and 'systemctl status Xvfb.service' for details.
polkit-agent-helper-1: pam_authenticate failed: Authentication failure
The command "if [[ "$TRAVIS_OS_NAME" == "linux" && "$HOSTTYPE" != "ppc64le" ]]; then sh ci/before_script_linux.sh; fi" failed and exited with 1 during .

[thaJeztah]

Hm.. looks like pass is failing with gpg2 (perhaps still something wrong with how it's initialised)

ok  	github.com/docker/docker-credential-helpers/credentials	0.006s
=== RUN   TestPassHelper
    pass_test.go:26: no usernames for https://foobar.docker.io:2376/v1
--- FAIL: TestPassHelper (0.10s)