Fixed positional order of arguments

The positional arguments of backup-create and configuration-attach
were different from all other commands.  'Instance' is now the
first argument for these commands as well.

DocImpact: This potentially affects any user scripts that may
exist.  Any instructions like:
'trove backup-create mybackup myinstance'
'trove configuration-attach myconfig myinstance'
should be changed to:
'trove backup-create myinstance mybackup.'
'trove configuration-attach myinstance myconfig'

Change-Id: I2ff93a1a6e26f3e33a60cbf3d9ad5ee074307e8f
Closes-Bug: #1281878
Merge "Fixed positional order of arguments"