Stop testing deprecated command nova-manage instance_type

'nova-manage instance_type' was deprecated in Havana, and in order to
remove it in Icehouse we have to stop testing it in gate.

Related to Ieb3775e0a43084d00624f9e1d8b879c312e32b3c

Change-Id: I1ca490593d3a61424b0000c6d64a541b2c9bd42c
remove skip bug 1233026

remove the skip bug 1233026 due to it has been fixed

Change-Id: I062c3d8919e33aea06dd271c064c9878b844cb26
Merge "remove skip bug 1233026"
Merge "Stop testing deprecated command nova-manage instance_type"