Added static Charset to QueryRequestMarshaller

QueryRequestMarshaller used a String.getBytes(“UTF-8”) which is
inefficient and locks in the NIO classes when used in highly threaded
situations. At the low level this is:

at sun.nio.cs.FastCharsetProvider.charsetForName(FastCharsetProvider.java:135)
	- waiting to lock <0x0000000092c6be68> (a sun.nio.cs.StandardCharsets)
	at java.nio.charset.Charset.lookup2(Charset.java:487)
	at java.nio.charset.Charset.lookup(Charset.java:475)
	at java.nio.charset.Charset.isSupported(Charset.java:517)
	at java.lang.StringCoding.lookupCharset(StringCoding.java:99)
	at java.lang.StringCoding.encode(StringCoding.java:336)
	at java.lang.String.getBytes(String.java:916)