Change canary back to start both worker and starter by default

[longquanzheng]

What changed?
Change canary back to start both worker and starter by default

Why?
In a previous PR, I changed the default to start worker only. I realized that this is a breaking change as some users told me they are using canary in some release version already. So it's better to not break them.

On another hand, I think starting worker only is useful for manual testing, which can be done already since we have the mode argument. But the default behavior should start all for simplicity.

How did you test it?
Local test

Potential risks

Release notes

Documentation Changes

[coveralls]

Pull Request Test Coverage Report for Build 19c819e5-315c-4fbf-8231-0308269a98ea

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 97 unchanged lines in 8 files lost coverage.
• Overall coverage decreased (-0.05%) to 56.795%

---

Files with Coverage Reduction	New Missed Lines	%
common/task/weightedRoundRobinTaskScheduler.go	2	89.12%
service/matching/matcher.go	2	91.46%
common/task/fifoTaskScheduler.go	4	83.51%
common/persistence/nosql/nosqlplugin/cassandra/workflow.go	6	55.04%
common/persistence/nosql/nosqlplugin/cassandra/tasks.go	14	72.8%
common/persistence/nosql/nosqlTaskStore.go	16	58.37%
common/persistence/nosql/nosqlplugin/cassandra/workflowUtils.go	19	77.07%
common/persistence/nosql/nosqlplugin/cassandra/workflowParsingUtils.go	34	83.58%

Totals
Change from base Build 92a85973-ef4a-4778-ba60-ab65303ea4cf:	-0.05%
Covered Lines:	81478
Relevant Lines:	143459

---

💛 - Coveralls