[10665][patch] class specific base reputation correction at vendors

[emsy]

* What bug does the patch fix? What features does the patch add?

A known bug related to death knights and ebon blade, where they needed 3000 more reputation then it is actually required. (f.e. for items requiring revered reputation they needed 3000/21000). This happened because they start at 3000 base reputation with Ebon Blade faction and it is (unlike for mages and Kirin tor) defined with zero racemask in DBC.

* For which repository revision was the patch created?

Mangos 10657 HEAD b573b33a48319679b8446a2c1c518afa4f4c6976

http://paste2.org/p/1062220

[VladimirMangos]

In [10665]. Thank you

I also move selection code in helper function.