Fix useless error message

The error message

"Error 1: Error code is not set"

has no useful information in this case. LTKLinuxUtil::loadSharedLib does
only return the values FAILURE or SUCCESS. No useful error text can be
displayed from that.

Change-Id: Ic1e00ad6a68dd14eddbe7e103a37190643b75270
Reviewed-by: Mitch Curtis <mitch.curtis@theqtcompany.com>
Reviewed-by: Jarkko Koivikko <jarkko.koivikko@code-q.fi>