PPO2: Call total_episode_reward_logger before incrementing num_timesteps

[balintkozma]

Description

In ppo2.py total_episode_reward_logger should be called before incrementing num_timesteps. See explanation in #143.

Motivation and Context

It improves the reported episode reward logging issue, and a PR was asked.

• I have raised an issue to propose this change (required for new features and bug fixes)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (update in the documentation)

Checklist:

• I've read the CONTRIBUTION guide (required)
• I have updated the changelog accordingly (required).
• My change requires a change to the documentation.
• I have updated the tests accordingly (required for a bug fix or a new feature).
• I have updated the documentation accordingly.

[araffin]

Hello,

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