Improve debug message "Skipping legacy bootloaders on UEFI system"

[Karl-Philipp Richter]

I'd be more helpful if messages in the form of `20microsoft: debug: Skipping legacy bootloaders on UEFI system` would say `20microsoft: debug: Skipping legacy bootloaders file0, file1, file2 on UEFI system /path/to/basedir`.

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: grub2 (not installed)
Uname: Linux 3.19.3-031903-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.17-0ubuntu1
Architecture: amd64
CurrentDesktop: Unity
Date: Tue Apr 7 01:28:45 2015
EcryptfsInUse: Yes
InstallationDate: Installed on 2015-04-02 (4 days ago)
InstallationMedia: Ubuntu 15.04 "Vivid Vervet" - Beta amd64 (20150326)
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: grub2
UpgradeStatus: No upgrade log present (probably fresh install)

[Marcus Tomlinson (marcustomlinson)]

This release of Ubuntu is no longer receiving maintenance updates. If this is still an issue on a maintained version of Ubuntu please let us know.

[Launchpad Janitor (janitor)]

[Expired for grub2 (Ubuntu) because there has been no activity for 60 days.]