TLS handshake errors produce log messages with a slightly different log format

[nkissebe]

Relatively minor issue, and maybe its buried to far in a go library to change, but:

TLS handshake errors produce log messages with a slightly different log format than messages coming from vault.

Normal log messages:
2018-08-15T11:04:09.918-0400 [INFO ] expiration: lease restore complete

TLS handshake errors:
2018-08-15 11:04:10.025470 I | http: TLS handshake error from 10.65.243.28:29075: EOF

The date format is slightly different, and the debug level is indicated differently. If not expected this could make automatic log monitoring do something unexpected.