Fix unitialized variable in `zstream redup` command
Fix uninitialized variable in `zstream redup` command. The compiler
may determine the 'stream_offset' variable can be uninitialized
because not all rdt_lookup() exit paths set it. This should never
happen in practice as documented by the assert, but initialize it
regardless to resolve the warning.
Reviewed-by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #10241
Closes #10244