udisks: fix build with newer glibc versions

udisks: fix build with newer glibc versions

Backport an upstream patch to fix the build with newer glibc versions.
This is how the failure looks like:

job-drive-detach.c: In function 'sysfs_exists':
job-drive-detach.c:44:15: error: storage size of 'statbuf' isn't known
   struct stat statbuf;

Fixes:

  http://autobuild.buildroot.net/results/ab3/ab36c2a1d2ca41a4d9ec6bab7d8d45678dbc5dcd/

Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>