Conditional check for tty/non-tty in case of wait (i.e. read)

[s1061123]

Fix #615.

[s1061123]

Here's the sample output of tty -s

$ docker run --entrypoint="" centos/tools /bin/bash -c 'if tty -s; then echo "tty"; read; else echo "not TTY"; sleep 3; fi'
not TTY
$ docker run -t --entrypoint="" centos/tools /bin/bash -c 'if tty -s; then echo "tty"; read; else echo "not TTY"; sleep 3; fi'
tty

[coveralls]

Pull Request Test Coverage Report for Build 599854235

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 70.694%

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Totals
Change from base Build 595134999:	0.0%
Covered Lines:	1141
Relevant Lines:	1614

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💛 - Coveralls

[dougbtv]

LGTM!