feat: Allow replicas to be set to zero

In some cases, we want to set replicas to zero, such as when we want
perform DB dump for migration to a new DB.

Add test for testing that a fraction of a non-zero replica (for
incremental rollouts) have a floor of 1.
22 jobs for get_replicas_zero in 4 minutes and 23 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #453168875
build

00:01:12

 
  Test
passed #453168896
test-create-application-secret

00:00:37

passed #453168890
test-create-secret

00:00:44

passed #453168891
test-create-secret-public-project

00:00:42

passed #453168878
test-dependencies

00:00:41

passed #453168894
test-deploy

00:01:40

passed #453168895
test-deploy-modsecurity

00:01:18

passed #453168883
test-deploy-name

00:00:42

passed #453168882
test-download-chart

00:01:09

passed #453168888
test-ensure-namespace

00:00:43

passed #453168884
test-get-replicas

00:00:46

passed #453168886
test-get-replicas-fraction

00:00:32

passed #453168885
test-get-replicas-multiple

00:00:40

passed #453168887
test-get-replicas-zero

00:00:47

passed #453168889
test-initialize-tiller

00:00:41

passed #453168879
test-kube-domain

00:00:39

passed #453168880
test-kube-domain-legacy

00:00:43

passed #453168881
test-kube-domain_error

00:00:42

passed #453168892
test-persist-environment-url

00:00:39

passed #453168876
test-shellcheck

00:00:20

passed #453168877
test-shfmt

00:00:20

 
  Release
passed #453168897
publish-dryrun

00:01:27