use role name rather than token displayname in generated mysql usernames
use role name rather than token displayname in generated mysql usernames

If a single token generates multiple myself roles, the generated mysql
username was previously prepended with the displayname of the vault
user; this makes the output of `show processlist` in mysql potentially
difficult to correlate with the roles actually in use without cross-
checking against the vault audit log.

See https://github.com/hashicorp/vault/pull/1603 for further discussion.

deverton/hashicorp-vault,danielsomerfield/vault,martin-ducar-gd/vault,quixoten/vault,rnaveiras/vault,deverton/hashicorp-vault,rnaveiras/vault,quixoten/vault,lirao/vault,Aloomaio/vault,quixoten/vault,Caiyeon/vault,wjam/vault,kingland/vault,martin-ducar-gd/vault,hashicorp/vault,rnaveiras/vault,MonsantoCo/vault,hartsock/vault,hartsock/vault,lemondrank/vault,kingland/vault,lemondrank/vault,hashicorp/vault,mgk/vault,hartsock/vault,jgcallero/vault,michaelansel/vault,cimarron-pistoncloud/vault,joelthompson/vault,ryon/vault,Aloomaio/vault,wjam/vault,tallpauley/vault,jmhardison/vault,jam-pot/vault,mymercurialsky/vault,doodles526/vault,kingland/vault,memory/vault,MonsantoCo/vault,hashicorp/vault,Aloomaio/vault,Banno/vault,jgcallero/vault,memory/vault,jmhardison/vault,danielsomerfield/vault,naunga/vault,kingland/vault,Banno/vault,quixoten/vault,skippy/vault,doodles526/vault,mymercurialsky/vault,hashicorp/vault,skippy/vault,kingland/vault,joelthompson/vault,hartsock/vault,mgk/vault,mgk/vault,Caiyeon/vault,jmhardison/vault,mgk/vault,chrishoffman/vault,mhurne/vault,jmhardison/vault,cimarron-pistoncloud/vault,rnaveiras/vault,ryon/vault,tallpauley/vault,peteryhwong/vault,naunga/vault,LolalyLuo/vault,jmhardison/vault,mhurne/vault,Aloomaio/vault,hashicorp/vault,LolalyLuo/vault,chrishoffman/vault,hashicorp/vault,hartsock/vault,joelthompson/vault,michaelansel/vault,lirao/vault,jam-pot/vault,peteryhwong/vault,joelthompson/vault,rnaveiras/vault