MB-11567: Pass bucket name and password from environment variables

Windows will have different interpretation on cmd arguments from Linux.
If empty password is passed, the next argument is treated as password.
As such, environment variable is better place to pass bucket credentials.

Change-Id: Ic096d9c7474982ed609aece6b721185a21d13e9c
Reviewed-on: http://review.couchbase.org/41293
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Bin Cui <bin.cui@gmail.com>