fix: Use error condition when active platform cannot be resolved

[jamesnetherton]

Small follow up on #810.

@lburgazzoli we talked a little about this. If there was an error resolving the active platform, then we are by definition 'waiting for platform'. This change enforces that and if necessary, creates an error condition to explain why we are waiting. E.g:

  status:
    conditions:
    - lastTransitionTime: 2019-07-12T10:08:04Z
      lastUpdateTime: 2019-07-12T10:08:04Z
      message: no active integration platforms found in the namespace
      reason: IntegrationPlatformAvailable
      status: "False"
      type: IntegrationPlatformAvailable
    digest: v9FqdLzzwPOMriNhXst9VMIssvvQ4KFBdbBY9K2v29ps
    phase: Waiting For Platform

This fixes the remaining e2e tests are currently failing.