Fixes #14586

The error returned by client.Upload was previously being ignored due to becoming
out of scope outside the if statement. This has been fixed by instead defining a
function which returns the hash and error (rather than trying to set the hash in
each branch of the if statement).

core: Fix VM error logging

Signed-off-by: Lewis Marshall <lewis@lmars.net>

core/vm: Use a bitmap instead of a map for jumpdest analysis

t push --force

This PR adds a Swarm development environment which can be run in a
Docker container and provides scripts for building binaries and running
Swarm clusters.

accounts/keystore, crypto: don't enforce key checks on existing keyfiles

core: reduce transaction reorganization overhead

ethstats: reduce ethstats traffic by trottling reports

cotnainers/docker: fix the legacy alpine image before dropping

internal/ethapi: add mutex around signing + nonce assignment

This prevents concurrent assignment of identical nonces when automatic
assignment is used.