rez overwrites root logger

[nerdvegas]

Rez logging conf is applied via init.py, and root logger handles are cleared. This has caused a problem in an unrelated package using the rez package.

Logging should be setup in cli tools only, everywhere else should just use loggers created via logging.getLogger(). Rez logging is a bit of a mess and needs an overhaul, however initially and in the interests of backwards compatibility, imo the fix should just:

• set "rez" logger to propagate=False
• not set root logger