HPCC-9112 When the user sprays a set of files using wildcards in dfuplus, only
the first 14980 files are getting sprayed.

Fix for HPCC-9112 issue.

This change modify he CRemoteDirectoryIterator::appedBuf() to proper handle
end of stream and end of block conditions. Before this fix if the directory
contents spanned more than one transfer buffer between nodes, only the first
buffer content iterated by the next() because the block_end_flag inserted
the buffer and he next() interpreted it to 'no_more_valid_item flag.
This fix removes the block_end_flags.

It also change a variable name from "b" to "isValidEntry" in the
CRemoteDirectoryIterator::next() method to improve code self documentation.

Finally it changes some information text message in dfuplus.cpp  because same
log generated in two different function (fixedSpray and variableSpray).

Signed-off-by: Attila Vamos <attila.vamos@gmail.com>