"Can not perform this action after onSaveInstanceState" on attachRouter

From a crash report in our production app:

```
android.app.FragmentManagerImpl.checkStateLoss (FragmentManager.java:1858)
android.app.FragmentManagerImpl.enqueueAction (FragmentManager.java:1881)
android.app.BackStackRecord.commitInternal (BackStackRecord.java:688)
android.app.BackStackRecord.commit (BackStackRecord.java:646)
com.bluelinelabs.conductor.internal.LifecycleHandler.install (LifecycleHandler.java:74)
com.bluelinelabs.conductor.Conductor.attachRouter (Conductor.java:36)
```

Conductor 2.1.5
Android 8.1.0
Device: WIKO W_K300

This seems to happen at app startup, from ```onCreate``` on that line

```
mActivityRouter = Conductor.attachRouter(this, mViewGroupContainer, poSavedInstanceState);
```

Start at Conductor.attachRouter and follow the reported stack into LifecycleHandler.install, then compare that path with the Activity.onCreate call shown in the report and its saved-instance-state argument. Reproduce the startup sequence if possible and determine the conditions that cause the FragmentManager state-loss exception; done means the reported attachRouter startup path no longer crashes, with the behavior verified on a relevant Android environment.

Written by the indexing model from the issue text.