Add midway2/3 partition/qos

[shenyangshi]

A small change that makes the automatic differentiation between midway3 and midway2.

[coveralls]

Pull Request Test Coverage Report for Build 8884113640

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 91.979%

---

Totals
Change from base Build 8848981890:	0.0%
Covered Lines:	1548
Relevant Lines:	1683

---

💛 - Coveralls

[dachengx]

Maybe we should:

1. add a condition for midway2 and midway3
2. warn the user if the hostname is not understandable and assign nothing

[shenyangshi]

excluded_nodes as null is added as default for midway3, as without an explicit excluded_nodes, midway3 job submission will yield error.