utils: aa-genprof fails on lxd with OSError: Read-only file system

On certain lxc containers, when aa-genprof tries to set
printk_ratelimit, it fails with the OSError exception, with the
message "OSError: [Errno 30] Read-only file system" instead of
PermissionError.

Since PermissionError is a subclass of OSError, replace it by broader
OSError exception to include both cases in which running aa-genprof
fails.

Reported-by: Paulo Flabiano Smorigo <paulo.smorigo@canonical.com>
Signed-off-by: Georgia Garcia <georgia.garcia@canonical.com>

utils/aa-genprof

@@ -139,7 +139,7 @@ ratelimit_saved = sysctl_read(ratelimit_sysctl)
 
 try:
     sysctl_write(ratelimit_sysctl, 0)
-except PermissionError:  # will fail in lxd
+except OSError:  # will fail in lxd
     warn("Can't set printk_ratelimit, some events might be lost")
 
 atexit.register(restore_ratelimit)