Stop logging paramiko's DEBUG and INFO messages

When ironic-conductor is run in debug mode with the SSH power driver,
Paramiko logs spurious DEBUG and INFO messages constantly. There is
already sufficient logging within the SSH power driver.

This patch adds paramiko to the list of modules who should only be
logged at or above a WARN level, even in debug mode.

Change-Id: Iccdfebbdc344c33c8fc0ab81f3ab5a176cd43a17
Merge "Stop logging paramiko's DEBUG and INFO messages"