Default GlanceLogFile template parameter value

The default for GlanceLogFile should be '', not an empty string;
however the UI code reads the default as an empty string.

Other parameters that default '' *should* be an empty string, so
there's no universal workaround on the UI side.

Change-Id: I4ba2fa76205f9d61572f7376f7dbaabde939a452
Merge "Default GlanceLogFile template parameter value"