_GetElementsFromLabelThread built its cleartool command with an

inverted condition: the branch handling a real label was guarded by

if self.label is None, which never happens, and the branch that always

ran replaced the command list outright, dropping cleartool find -avobs and

leaving just ['-exec', ...]. Running that raised an exception in the

thread, so label comparisons silently saw no elements and treated every

file as /main/0.
The special-case branch is now keyed off the "LATEST" pseudo-label

(which is not a real label type, and compares against the versions

selected by the view), and both branches append to the base find command

instead of replacing it.
This also strips each output line before parsing. The old execute()

based code split on newlines, but readlines() keeps them, which left a

trailing newline in every stored version string.

Added unit tests for the thread with a label and with LATEST.
Ran unit tests.