Merge branch 'net-explicitly-requires-bash-when-needed'

Paolo Abeni says:

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net: explicitly requires bash when needed.

Some test scripts require bash-only features but use the default shell.
This may cause random failures if the default shell is not bash.
Instead of doing a potentially complex rewrite of such scripts, these patches
require the bash interpreter, where needed.
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Signed-off-by: David S. Miller <davem@davemloft.net>