When changing templates, it's can be pretty time-intensive to
repair all test fixtures.
This change instruments CLI tests with two flags, `-update` and
`-pretty-diff` that control how test fixtures are diffed. When the
`-update` flag is set, the tests fixtures are overwritten as tests
execute. The `-pretty-diff` flag causes the full text of the fixture
to be printed on mismatch.
This introduces a `linkerd install-sp` command to install service
profiles into the linkerd control plane. It installs one service profile
for each of controller-api, proxy-api, prometheus, and grafana.
Fixes#1901
Signed-off-by: Andrew Seigner <siggy@buoyant.io>