Remove redefinition of is_win function
Remove redefinition of is_win function

We're already importing this from ccmlib.common here. In
zero tests do we ever use the dtest implementation, only ever the
ccmlib one. They're identical code.

stef1927/cassandra-dtest,beobal/cassandra-dtest,iamaleksey/cassandra-dtest,blerer/cassandra-dtest,krummas/cassandra-dtest,iamaleksey/cassandra-dtest,krummas/cassandra-dtest,pauloricardomg/cassandra-dtest,snazy/cassandra-dtest,thobbs/cassandra-dtest,mambocab/cassandra-dtest,riptano/cassandra-dtest,bdeggleston/cassandra-dtest,spodkowinski/cassandra-dtest,carlyeks/cassandra-dtest,aweisberg/cassandra-dtest,beobal/cassandra-dtest,pauloricardomg/cassandra-dtest,carlyeks/cassandra-dtest,pcmanus/cassandra-dtest,mambocab/cassandra-dtest,aweisberg/cassandra-dtest,snazy/cassandra-dtest,bdeggleston/cassandra-dtest,riptano/cassandra-dtest,thobbs/cassandra-dtest,spodkowinski/cassandra-dtest,blerer/cassandra-dtest,stef1927/cassandra-dtest