btrfs-progs: improve troubleshooting avoid duplicate error strings

btrfs-progs: improve troubleshooting avoid duplicate error strings

my troubleshooting experience says have unique error string per module.

In the below eg, its one additional step to know error line,

cat -n cmds-device.c | egrep "error removing the device"
   185	"ERROR: error removing the device '%s' - %s\n",
   190	"ERROR: error removing the device '%s' - %s\n",

which is completely avoidable.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
[merged the two messages into one]
Signed-off-by: David Sterba <dsterba@suse.cz>