Merge additional testcases and improvements to bin/ls/ls_tests from
^/user/ngie/more-tests.

• Additional testcases added:
  • ls -D
  • ls -F
  • ls -H
  • ls -L
  • ls -R
  • ls -S
  • ls -T
  • ls -b
  • ls -d
  • ls -f
  • ls -g
  • ls -h
  • ls -i
  • ls -k
  • ls -l
  • ls -m
  • ls -n
  • ls -o
  • ls -p
  • ls -q/ls -w
  • ls -r
  • ls -s
  • ls -t
  • ls -u
  • ls -y
• Socket file creation is limited to the ls -F testcase, greatly speeding up the test process
• The ls -C testcase was made more robust by limiting the number of columns via COLUMNS and by dynamically formulating the columns/lines.
• Add atf_test_case before all testcase head functions.

X-MFC with: r284388, r288330, r288423
MFC after: 2 weeks
Sponsored by: EMC / Isilon Storage Division