AccumuloClassLoader is being used in client API to create RFiles

[mikewalch]

While the creating an RFile in bulk import randomwalk test, the follow warnings were printed.

2018-11-28 16:20:29,126 [start.classloader.AccumuloClassLoader] WARN : Failed to load Accumulo configuration 'accumulo.properties' from classpath
2018-11-28 16:20:29,126 [start.classloader.AccumuloClassLoader] WARN : Using default value '/tmp' for 'general.vfs.cache.dir' as there is no Accumulo configuration on classpath
2018-11-28 16:20:29,128 [start.classloader.AccumuloClassLoader] WARN : Using default value 'null' for 'general.classpaths' as there is no Accumulo configuration on classpath
2018-11-28 16:20:29,128 [start.classloader.AccumuloClassLoader] WARN : Using default value '' for 'general.vfs.classpaths' as there is no Accumulo configuration on classpath
2018-11-28 16:20:29,129 [start.classloader.AccumuloClassLoader] WARN : Using default value '$ACCUMULO_HOME/lib/ext/[^.].*.jar' for 'general.dynamic.classpaths' as there is no Accumulo configuration on classpath
2018-11-28 16:20:29,131 [start.classloader.AccumuloClassLoader] WARN : Using default value '/tmp' for 'general.vfs.cache.dir' as there is no Accumulo configuration on classpath

Should probably avoid using accumulo-start module code in API.

[keith-turner]

I saw this while working on #782 yesterday and I was actually working on a fix.