Fix two bugs relating to --isolated missing and .isolate file being copied.

Fix two bugs relating to --isolated missing and .isolate file being copied.

Using isolate.py run without --isolated would crash.

If a user copy (and not move) a .isolate file from one location to another,
silently drop the saved state instead of throwing an exception.

Add unit test for both issues.

R=vadimsh@chromium.org
BUG=

Committed: https://code.google.com/p/swarming/source/detail?repo=client&r=8472efa

[vadimsh, 2014-03-18 18:12:16]

lgtm

https://codereview.appspot.com/77480043/diff/1/isolate.py
File isolate.py (right):

https://codereview.appspot.com/77480043/diff/1/isolate.py#newcode869
isolate.py:869: complete_state = CompleteState(None, SavedState(os.getcwd()))
maybe temp dir instead if it makes sense?

[M-A, 2014-03-18 18:31:32]

https://codereview.appspot.com/77480043/diff/1/isolate.py
File isolate.py (right):

https://codereview.appspot.com/77480043/diff/1/isolate.py#newcode869
isolate.py:869: complete_state = CompleteState(None, SavedState(os.getcwd()))
On 2014/03/18 18:12:16, vadimsh wrote:
> maybe temp dir instead if it makes sense?

I contemplated this idea but decided against. If the tool were to output junk by
accident, it would be in the current directory and very visible. In the temp
dir, it would simply accumulate.

[vadimsh, 2014-03-18 18:32:14]

On 2014/03/18 18:31:32, M-A wrote:
> https://codereview.appspot.com/77480043/diff/1/isolate.py
> File isolate.py (right):
> 
> https://codereview.appspot.com/77480043/diff/1/isolate.py#newcode869
> isolate.py:869: complete_state = CompleteState(None, SavedState(os.getcwd()))
> On 2014/03/18 18:12:16, vadimsh wrote:
> > maybe temp dir instead if it makes sense?
> 
> I contemplated this idea but decided against. If the tool were to output junk
by
> accident, it would be in the current directory and very visible. In the temp
> dir, it would simply accumulate.

okay :)

[M-A, 2014-03-18 18:33:02]

Committed patchset #1 manually as r8472efa (presubmit successful).