SUSE config: use Btrfs LZO compression for ResourceDisk

Btrfs provides support for transparent compression, which can be
requested at mount time via the compress=type[:level] mount option.

As demonstrated in [1], transparent LZO compression provides a good
trade-off between compression ratio and performance, while also being
supported by legacy SUSE kernels. zstd could be considered for
modern SLE15-SP1+ / openSUSE Leap 15.1+ kernels.

Amongst other benefits, moving from ext4 to Btrfs allows for ephemeral
ResourceDisk data to be periodically and incrementally backed-up to
regular Page Blob backed disks using btrfs send/recv.

1. Btrfs compression benchmarks
   mainline kernel commit: 5c1aab1dd5445ed8bdcdbb575abc1b0d7ee5b2e7

Signed-off-by: David Disseldorp <ddiss@suse.de>

config/suse/waagent.conf

@@ -43,7 +43,7 @@ ResourceDisk.Format=y
 
 # File system on the resource disk
 # Typically ext3 or ext4. FreeBSD images should use 'ufs2' here.
-ResourceDisk.Filesystem=ext4
+ResourceDisk.Filesystem=btrfs
 
 # Mount point for the resource disk
 ResourceDisk.MountPoint=/mnt/resource
@@ -55,7 +55,7 @@ ResourceDisk.EnableSwap=n
 ResourceDisk.SwapSizeMB=0
 
 # Comma-separated list of mount options. See mount(8) for valid options.
-ResourceDisk.MountOptions=None
+ResourceDisk.MountOptions=compress=lzo
 
 # Respond to load balancer probes if requested by Microsoft Azure.
 LBProbeResponder=y