FIX: Redirect App Output from StdErr to StdOut in Integration Tests

[Pantani]

The app output in the integration tests is going to the StdErr. We should check if everything is always going to the StdErr and fix

E.g.:

apps/examples/health-monitor/integration/app_test.go

Line 50 in b54b50d

step.Stderr(output),

apps/examples/hello-world/integration/app_test.go

Line 48 in b54b50d

step.Stderr(buf),

apps/examples/chain-info/integration/app_test.go

Line 49 in b54b50d

step.Stderr(buf),

apps/marketplace/integration/list_test.go

Line 50 in b54b50d

step.Stderr(buf),

[Pantani]

The problem was solved, but the integration tests for the explorer apps are showing the stdout into the stderr, but only in the tests; we should investigate later