checkarray --all only processes one array if scheduling class not specified

If --all given but no scheduling class specified only one array is checked. This appears to be because at lines 194-200 the variable ionice is checked. If no class is given then this is blank and the script exits.

Either a default should be used or validation included to check a class has been given.

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: mdadm 3.3-2ubuntu1
ProcVersionSignature: Ubuntu 3.19.0-22.22-generic 3.19.8-ckt1
Uname: Linux 3.19.0-22-generic x86_64
ApportVersion: 2.17.2-0ubuntu1.1
Architecture: amd64
Date: Sat Jul 11 14:57:58 2015
InstallationDate: Installed on 2015-06-12 (29 days ago)
InstallationMedia: Kubuntu 15.04 "Vivid Vervet" - Release amd64 (20150422)
MDadmExamine.dev.sda:
 /dev/sda:
    MBR Magic : aa55
 Partition[0] : 4294967295 sectors at 1 (type ee)
MDadmExamine.dev.sda2: Error: command ['/sbin/mdadm', '-E', '/dev/sda2'] failed with exit code 1: mdadm: No md superblock detected on /dev/sda2.
MDadmExamine.dev.sda4: Error: command ['/sbin/mdadm', '-E', '/dev/sda4'] failed with exit code 1: mdadm: No md superblock detected on /dev/sda4.
MDadmExamine.dev.sda7: Error: command ['/sbin/mdadm', '-E', '/dev/sda7'] failed with exit code 1: mdadm: No md superblock detected on /dev/sda7.
MDadmExamine.dev.sda8: Error: command ['/sbin/mdadm', '-E', '/dev/sda8'] failed with exit code 1: mdadm: No md superblock detected on /dev/sda8.
MDadmExamine.dev.sdb:
 /dev/sdb:
    MBR Magic : aa55
 Partition[0] : 2930277167 sectors at 1 (type ee)
MDadmExamine.dev.sdb2: Error: command ['/sbin/mdadm', '-E', '/dev/sdb2'] failed with exit code 1: mdadm: No md superblock detected on /dev/sdb2.
MDadmExamine.dev.sdb4: Error: command ['/sbin/mdadm', '-E', '/dev/sdb4'] failed with exit code 1: mdadm: No md superblock detected on /dev/sdb4.
MachineType: Gigabyte Technology Co., Ltd. To be filled by O.E.M.
ProcEnviron:
 LANGUAGE=en_GB:en
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_GB.UTF-8
 SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.19.0-22-generic root=UUID=f32dfa71-d154-4f81-9515-bef34b96bc2a ro quiet splash nomdmonddf nomdmonisw vt.handoff=7
SourcePackage: mdadm
UdevLog: Error: [Errno 2] No such file or directory: '/var/log/udev'
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 08/31/2012
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: F2
dmi.board.asset.tag: To be filled by O.E.M.
dmi.board.name: F2A85X-UP4
dmi.board.vendor: Gigabyte Technology Co., Ltd.
dmi.board.version: x.x
dmi.chassis.asset.tag: To Be Filled By O.E.M.
dmi.chassis.type: 3
dmi.chassis.vendor: Gigabyte Technology Co., Ltd.
dmi.chassis.version: To Be Filled By O.E.M.
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrF2:bd08/31/2012:svnGigabyteTechnologyCo.,Ltd.:pnTobefilledbyO.E.M.:pvrTobefilledbyO.E.M.:rvnGigabyteTechnologyCo.,Ltd.:rnF2A85X-UP4:rvrx.x:cvnGigabyteTechnologyCo.,Ltd.:ct3:cvrToBeFilledByO.E.M.:
dmi.product.name: To be filled by O.E.M.
dmi.product.version: To be filled by O.E.M.
dmi.sys.vendor: Gigabyte Technology Co., Ltd.
etc.blkid.tab: Error: [Errno 2] No such file or directory: '/etc/blkid.tab'