gologger: Use properly-formatted calls.
gologger: Use properly-formatted calls.

This fixes an issue with gologger, whose API incompatibly offers "Error"
and "Errorf". While past versions have had identical function
signatures, the API is starting to diverse more towards fmt.

BUG=

Review URL: https://codereview.chromium.org/1678323002

luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go