Revert "collectd: Use libstatgrab for reading disk stats"

This reverts commit 86beff5f75.

This patch breaks reading statistics on systems running a 4.14 kernel.
It seems like it is not dependant on the kernel, though.

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>

src/patches/collectd-4.10-disk-plugin-fields.patch

@@ -1,13 +0,0 @@
-diff --git a/src/disk.c b/src/disk.c
-index 4a78f1bd..c6f9e4bd 100644
---- a/src/disk.c
-+++ b/src/disk.c
-@@ -428,7 +428,7 @@ static int disk_read (void)
- 	IOObjectRelease (disk_list);
- /* #endif HAVE_IOKIT_IOKITLIB_H */
- 
--#elif KERNEL_LINUX
-+#elif 0
- 	FILE *fh;
- 	char buffer[1024];
-