[gnome-settings-daemon] build: Rebase recent libgnome-volume-control

[Bastien Nocera <hadess src gnome org>]

commit f06b1c3c9aa8e70e4b6d120a68f697956243dead
Author: Iñigo Martínez <inigomartinez gmail com>
Date:   Sat Feb 3 10:48:27 2018 +0100

    build: Rebase recent libgnome-volume-control
    
    Recent changes in libgnome-volume-control include some fixes and
    a number of build improvements. However, none of them make a major
    change that could affect gnome-settings-daemon, so these are nice
    to have improvements.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=793087

 subprojects/gvc |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/subprojects/gvc b/subprojects/gvc
index ce8e488..6a0ac9b 160000
--- a/subprojects/gvc
+++ b/subprojects/gvc
@@ -1 +1 @@
-Subproject commit ce8e4880ce31e275c40825c4ed756c791107f810
+Subproject commit 6a0ac9ba69f84d763f286c5741b57ff8d87c1f45