8214195: Align stdout messages in test/jdk/java/math/BigInteger/PrimitiveConversionTests.java

[Brian Burkhalter]

https://bugs.openjdk.java.net/browse/JDK-8214195
http://cr.openjdk.java.net/~bpb/8214195/webrev.00/

Print statements are different for float and double but should be the same.

Thanks,

Brian