Fixed issue for JDK8 in BSONOldTest.testUTF8. Now using only valid digits or letters.
Fixed issue for JDK8 in BSONOldTest.testUTF8. Now using only valid digits or letters.

kay-kim/mongo-java-driver,jyemin/mongo-java-driver,PSCGroup/mongo-java-driver,jsonking/mongo-java-driver,jyemin/mongo-java-driver,rozza/mongo-java-driver,jsonking/mongo-java-driver,rozza/mongo-java-driver,gianpaj/mongo-java-driver