Keep original file if -c or --stdout is given

Keep original file if -c or --stdout is given

Set removeSrcFile back to false when -c or --stdout is used to improve
compatibility with gzip(1) behavior.

gzip(1) is removing the original file on compression unless --stdout or
/-c is used. zstd is defaulting to keep the file unless --rm is used or
when it is called via a gzip symlink, in which it is removing by
default. Specifying -c/--stdout turns this behavior off.