PEP8: whitespace cleanup

ntpclients/ntpviz.py:61:15: W291 trailing whitespace
ntpclients/ntpviz.py:64:16: W291 trailing whitespace
ntpclients/ntpviz.py:66:5: E301 expected 1 blank line, found 0
pylib/agentx.py:111:1: E302 expected 2 blank lines, found 0
pylib/agentx.py:112:1: E302 expected 2 blank lines, found 0
pylib/agentx.py:1349:1: E302 expected 2 blank lines, found 1
pylib/statfiles.py:195:1: W293 blank line contains whitespace
pylib/statfiles.py:204:5: E303 too many blank lines (2)
tests/pylib/test_agentx.py:2522:27: E203 whitespace before ':'
tests/wscript:4:1: E302 expected 2 blank lines, found 1