[gparted] Provide comment for btrfs::clear_cache() call

[Curtis Gedak <gedakc src gnome org>]

commit d405bb22645ce72a235d3ad3346b9cc6a4f0c9f9
Author: Mike Fleetwood <mike fleetwood googlemail com>
Date:   Mon Jun 8 17:53:24 2015 +0100

    Provide comment for btrfs::clear_cache() call
    
    Explain why the implementation uses a clear_cache() call, rather than a
    straight load_cache() call.  This commit from 2014-02-17 implemented
    incremental loading of the btrfs device cache:
        76e64f2905bdbe37c307bc9fab055f44914dc7b2
        Detect busy status of multi-device btrfs file systems (#723842)

 src/GParted_Core.cc |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/GParted_Core.cc b/src/GParted_Core.cc
index d5121af..c84c691 100644
--- a/src/GParted_Core.cc
+++ b/src/GParted_Core.cc
@@ -151,7 +151,7 @@ void GParted_Core::set_devices_thread( std::vector<Device> * pdevices )
        FS_Info fs_info( true ) ;  //Refresh cache of file system information
        DMRaid dmraid( true ) ;    //Refresh cache of dmraid device information
        LVM2_PV_Info::clear_cache();            // Cache automatically loaded if and when needed
-       btrfs::clear_cache() ;
+       btrfs::clear_cache();                   // Cache incrementally loaded if and when needed
 
        init_maps() ;