add deploy stabilize timer

[tejal29]

Related to #176

This PR is part of breaking up a larger PR (#2811) that improves logging for health check based deployment status checking:

• Removes duplicated error log when deployment health check failed.
• Adds timings output line for deploy health check phase in case it is successful:

Before

tejaldesai@@microservices (add_deploy_stable_timer)$ skaffold run --default-repo=gcr.io/tejal-test --status-check
Generating tags...
...
Starting deploy...
kubectl client version: 1.11+
kubectl version 1.12.0 or greater is recommended for use with Skaffold
 - deployment.apps/leeroy-web configured
 - service/leeroy-app configured
 - deployment.apps/leeroy-app configured
Deploy complete in 3.791356548s
Waiting for deployments to stabilize
You can also run [skaffold run --tail] to get the logs

After:

tejaldesai@@microservices (add_deploy_stable_timer)$ skaffold run --default-repo=gcr.io/tejal-test --status-check
Generating tags...
...
Starting deploy...
kubectl client version: 1.11+
kubectl version 1.12.0 or greater is recommended for use with Skaffold
 - deployment.apps/leeroy-web configured
 - service/leeroy-app configured
 - deployment.apps/leeroy-app configured
Deploy complete in 3.791356548s
Waiting for deployments to stabilize
Deployments stabilized in 6.059712568s
You can also run [skaffold run --tail] to get the logs

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@16e1b32). Click here to learn what that means.
The diff coverage is 66.66%.

Impacted Files	Coverage Δ
pkg/skaffold/runner/deploy.go	73.68% <66.66%> (ø)