Add codec and decodeerrors parameters to .run methods on SSHDriver and ShellDriver

[kjeldflarup]

Problem is described in this issue #203

This PR solves this by allowing the .run method for the SSHDriver and the ShellDriver to take extra arguments. All tests that have conflicting characters must be rewritten.

stdout, stderr, returncode = command.run("/tmp/pcm52test/test-registration", codec = "iso-8859-1" )
stdout, stderr, returncode = command.run("/tmp/pcm52test/test-registration", codecerrors = "ignore" )
stdout, stderr, returncode = command.run("/tmp/pcm52test/test-registration", codec = "iso-8859-1", codecerrors = "ignore" )

The parameters are passed to str.decode(), for more information on possible parameters see https://docs.python.org/3/howto/unicode.html

The defaults is "utf-8" and strict, which is also the defaults for str.decode(), and thus no existing tests will be affected by this PR.

[codecov-io]

Codecov Report

Merging #214 into master will increase coverage by <.1%.
The diff coverage is 42.8%.

@@           Coverage Diff            @@
##           master    #214     +/-   ##
========================================
+ Coverage    54.6%   54.6%   +<.1%     
========================================
  Files          93      93             
  Lines        5269    5270      +1     
========================================
+ Hits         2881    2882      +1     
  Misses       2388    2388

Impacted Files	Coverage Δ
labgrid/driver/sshdriver.py	38% <33.3%> (+0.5%)	⬆️
labgrid/driver/shelldriver.py	29% <50%> (ø)	⬆️

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[jluebbe]

I've changed some white-space and remote a leftover debug print().