chore(jest): change config to generate Cobertura coverage reports
chore(jest): change config to generate Cobertura coverage reports

Explicitly configure `coverageReporters ` to include the defaults  (
"json", "lcov", "text") as well as `cobertura` to generate Cobertura
coverage reports.

Closes DCOS-16515

dcos/dcos-ui,dcos/dcos-ui,dcos/dcos-ui,dcos/dcos-ui,dcos/dcos-ui