[commands] Fix attribute access in cogs to commands.
[commands] Fix attribute access in cogs to commands.

Previously they were outdated copies, this updates the copies to the
ones that are actually injected.

imayhaveborkedit/discord.py,khazhyk/discord.py,Harmon758/discord.py,Harmon758/discord.py,rapptz/discord.py,Rapptz/discord.py