Default to using pkg/log for all logging and use a fixed time prefix
which is RFC3339Millli (doesn't exist in time, so we just extended
RFC3339), i.e. Nano might be pushing it.

Logs go from:

2018/10/30 19:14:55 [INFO] CoreDNS-1.2.5
2018/10/30 19:14:55 [INFO] linux/amd64, go1.11,

to:

2018-10-30T19:10:07.547Z [INFO] CoreDNS-1.2.5
2018-10-30T19:10:07.547Z [INFO] linux/amd64, go1.11,

Which includes the timezone - which oddly the std log package doesn't
natively do.
Signed-off-by: Miek Gieben <miek@miek.nl>