micro-patch for setup-storage

[Thomas Neumann]

Hello Brian

> With your patches, an initial install of the attached MD_RAID1 + LVM 
> disk_config works, but a subsequent preserve_reinstall (without initial 
> flag) fails with a non-zero return code from "Executing: mdadm --stop 
> --scan".  Full output is attached.
[...]
> Might have something to do with the RAID not having finished rebuilding 
> yet.

I extracted a commandlist from your pastebin. Seems like the failing
command is the first one. Would be interesting to know which exit code
has been signaled. Try modifying Exec.pm::execute_command() but you may
have more luck kludging some output handler into the return function of
Exec.pm::execute_command_internal().

 23:mdadm --stop --scan
 24:mdadm --assemble --scan --config=/tmp/fai/mdadm-from-examine.conf
 26:mdadm -W --stop /dev/md0
 33:vgchange -a n vg
 34:lvremove -f vg/var
 35:lvremove -f vg/swap
 36:lvremove -f vg/root
 53:wipefs -a /dev/sdb1
 63:wipefs -a /dev/sda1
 73:mdadm -W --stop /dev/md1
 95:parted -s /dev/sdb mklabel msdos
 96:parted -s /dev/sdb mkpart primary "" 1048576B 235929599B
 98:parted -s /dev/sdb set 1 boot on
 99:parted -s /dev/sdb mkpart primary "" 235929600B 42949672959B
101:parted -s /dev/sdb set 2 raid on
104:parted -s /dev/sda mklabel msdos
105:parted -s /dev/sda mkpart primary "" 1048576B 235929599B
107:parted -s /dev/sda set 1 boot on
108:parted -s /dev/sda mkpart primary "" 235929600B 42949672959B
110:parted -s /dev/sda set 2 raid on
111:parted -s /dev/sda set 1 raid on
112:parted -s /dev/sdb set 1 raid on
130:yes | mdadm --create  /dev/md0 --level=raid1 --force --run --raid-devices=2 /dev/sda1 /dev/sdb1
131:mkfs.ext3 -L boot /dev/md0
132:tune2fs -c 90 -i 90d /dev/md0
133:mdadm --assemble /dev/md1 /dev/sdb2 /dev/sda2
136:vgchange -a y vg
137:lvcreate  -n swap -L 5980.71079758757 vg
138:mkswap -L swap /dev/vg/swap
139:lvcreate  -n root -L 10076.7107975876 vg
140:mkfs.ext4 -L root /dev/vg/root
141:tune2fs -c 90 -i 90d /dev/vg/root
142:lvcreate  -n var -L 10076.7107975876 vg
143:mkfs.ext4 -L var /dev/vg/var
144:tune2fs -c 90 -i 90d /dev/vg/var