Changed the keyword argument for runCmd()/expect() from 'verbose' to 'trace',

which, defaults to False, and if set to True, will trace lldb command execution
and result.

Added "-t" command option to the test driver dotest.py which sets the
LLDB_COMMAND_TRACE environment variable to "YES" and as a result always turns on
command tracing regardless of the 'trace' keyword argument to runCmd()/expect().

llvm-svn: 111811