1fe67f9 introduced retries to the ssh connection put file and fetch
file. Unfortunately, that change broke the smart transport because it
started raising exceptions instead of returning from _run(). This
breakage is documented in #23711.
An attempt to fix it was made at #23717 but the first attempt was
objected to as needing to touch too much code. The second attmept was
objected to as smart was forced to encapsulate retries (thus retrying
a sftp "rety" times before trying scp "retry" times and then finally
moving onto piped). This third attempt has retries encapsulate smart.
So each sub-transport is tried once and if all three fail, another retry
attempt is made which tries each of the three again.
Fixes#23711Fixes#23717
3edac559d3