Reduce livepeer image size

[cyberj0g]

A quick fix for reducing the size of the docker image: switched back to CUDA 10 for amd64 build. A proper fix would be to have:

1. An image for Broadcaster, which doesn't include ./lib/* from Tensorflow distribution, but compiles with Tensorflow headers to avoid the risks and added complexity of having binaries built with different configurations depending on node type
2. A separate Tensorflow image, which will additionally include ./lib/* from Tensorflow distribution

[codecov]

Codecov Report

Merging #2712 (62e137b) into master (a3949f3) will not change coverage.
The diff coverage is 0.00000%.

@@              Coverage Diff              @@
##              master       #2712   +/-   ##
=============================================
  Coverage   56.33265%   56.33265%           
=============================================
  Files             88          88           
  Lines          19131       19131           
=============================================
  Hits           10777       10777           
  Misses          7765        7765           
  Partials         589         589           

Impacted Files	Coverage Δ
server/ot_rpc.go	35.34483% <0.00000%> (ø)

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Impacted Files	Coverage Δ
server/ot_rpc.go	35.34483% <0.00000%> (ø)