disable requiretty for kitchen user

I faced following error on centos 5.8:
```
% kitchen setup
-----> Starting Kitchen (v1.2.1)
-----> Converging <default-centos-58>...
       Preparing files for transfer
       Resolving cookbook dependencies with Berkshelf 2.0.14...
       Removing non-cookbook files before transfer
-----> Installing Chef Omnibus (true)
       downloading https://www.getchef.com/chef/install.sh
         to file /tmp/install.sh
       trying curl...
         % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dlo
       ad  Upload   Total   Spent    Left  Speed
  0     0    0     0    0     0      0      0 --:--:--  0:0
100 14401  100 14401    0     0   6924      0         0:00:02  0:00:02 --:--:-- 54549
       sudo: sorry, you must have a tty to run sudo
>>>>>> Converge failed on instance <default-centos-58>.
>>>>>> Please see .kitchen/logs/default-centos-58.log for more details
>>>>>> ------Exception-------
>>>>>> Class: Kitchen::ActionFailed
>>>>>> Message: SSH exited (1) for command: [sh -c '
        # Check whether a command exists - returns 0 if it does, 1 if it does not
        exists() {
if command -v $1 >/dev/null 2>&1
then
  return 0
else
  return 1
fi
        }

        # do_wget URL FILENAME
        do_wget() {
echo "trying wget..."
wget -O "$2" "$1" 2>/tmp/stderr
# check for bad return status
test $? -ne 0 && return 1
# check for 404 or empty file
grep "ERROR 404" /tmp/stderr 2>&1 >/dev/null
if test $? -eq 0 || test ! -s "$2"; then
  return 1
fi
return 0
        }

        # do_curl URL FILENAME
        do_curl() {
echo "trying curl..."
curl -L "$1" > "$2"
# check for bad return status
[ $? -ne 0 ] && return 1
# check for bad output or empty file
grep "The specified key does not exist." "$2" 2>&1 >/dev/null
if test $? -eq 0 || test ! -s "$2"; then
  return 1
fi
return 0
        }

        # do_fetch URL FILENAME
        do_fetch() {
echo "trying fetch..."
fetch -o "$2" "$1" 2>/tmp/stderr
# check for bad return status
test $? -ne 0 && return 1
return 0
        }

        # do_perl URL FILENAME
        do_perl() {
echo "trying perl..."
perl -e "use LWP::Simple; getprint($ARGV[0]);" "$1" > "$2"
# check for bad return status
test $? -ne 0 && return 1
# check for bad output or empty file
# grep "The specified key does not exist." "$2" 2>&1 >/dev/null
# if test $? -eq 0 || test ! -s "$2"; then
#   unable_to_retrieve_package
# fi
return 0
        }

        # do_python URL FILENAME
        do_python() {
echo "trying python..."
python -c "import sys,urllib2 ; sys.stdout.write(urllib2.urlopen(sys.argv[1]).read())" "$1" > "$2"
# check for bad return status
test $? -ne 0 && return 1
# check for bad output or empty file
#grep "The specified key does not exist." "$2" 2>&1 >/dev/null
#if test $? -eq 0 || test ! -s "$2"; then
#  unable_to_retrieve_package
#fi
return 0
        }

        # do_download URL FILENAME
        do_download() {
PATH=/opt/local/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
export PATH

echo "downloading $1"
echo "  to file $2"

# we try all of these until we get success.
# perl, in particular may be present but LWP::Simple may not be installed

if exists wget; then
  do_wget $1 $2 && return 0
fi

if exists curl; then
  do_curl $1 $2 && return 0
fi

if exists fetch; then
  do_fetch $1 $2 && return 0
fi

if exists perl; then
  do_perl $1 $2 && return 0
fi

if exists python; then
  do_python $1 $2 && return 0
fi

echo ">>>>>> wget, curl, fetch, perl or python not found on this instance."
return 16
        }


should_update_chef() {
  case "true" in
    true|`chef-solo -v | cut -d " " -f 2`) return 1 ;;
    latest|*) return 0 ;;
  esac
}

if [ ! -d "/opt/chef" ] || should_update_chef ; then
  echo "-----> Installing Chef Omnibus (true)"
  do_download https://www.getchef.com/chef/install.sh /tmp/install.sh
  sudo -E sh /tmp/install.sh
fi'
]
>>>>>> ----------------------
```

This is because `Defaults requiretty` line in `/etc/sudoers`, so I disabled tty requirement for kitchen user.
It's same solution as [this comment](https://github.com/WASdev/ci.chef.wlp/issues/9#issuecomment-24597591).