Debugger breaks inside ptvsd
Test code:
```py
import ptvsd
ptvsd.enable_attach(None)

x = 1
while True:
    x += 1
    print(x)
```
Breakpoint set on `print`. After attaching, the stack is:
```
>	enable_attach in __init__ line 87	Python	Symbols loaded.
 	PythonApplication1 module line 7	Python	Symbols loaded.
```
where `__init__` is `ptvsd\\__init__.py`. The line in question is inside `enable_attach`. However, the line on which it's actually broken is the one with `print`. So the breakpoint is hit, which is correct, but the stack is weird.

The real problem here is that `__init__.py` is not in `DONT_DEBUG`.

diff --git a/Python/Product/PythonTools/ptvsd/attach_server.py b/Python/Product/PythonTools/ptvsd/attach_server.py
index 316a7386d..2394d0877 100644
--- a/Python/Product/PythonTools/ptvsd/attach_server.py
+++ b/Python/Product/PythonTools/ptvsd/attach_server.py
@@ -137,11 +137,9 @@ def enable_attach(secret, address=('0.0.0.0', ptvsd.DEFAULT_PORT), certfile=None
 
     frames = []
     f = sys._getframe()
-    while True:
-        f = f.f_back
-        if f is None:
-            break
+    while f is not None:
         frames.append(f)
+        f = f.f_back
     frames.reverse()
     cur_thread = vspd.new_thread()
     for f in frames:
diff --git a/Python/Product/PythonTools/ptvsd/debugger.py b/Python/Product/PythonTools/ptvsd/debugger.py
index 8a4f60cc6..e7407ea03 100644
--- a/Python/Product/PythonTools/ptvsd/debugger.py
+++ b/Python/Product/PythonTools/ptvsd/debugger.py
@@ -43,6 +43,7 @@ import runpy
 import datetime
 from codecs import BOM_UTF8
 
+import ptvsd
 import ptvsd.util as _vspu
 import ptvsd.ipcjson as _vsipc
 import ptvsd.repl as _vspr
@@ -155,7 +156,13 @@ class SynthesizedValue(object):
 
 # Specifies list of files not to debug. Can be extended by other modules
 # (the REPL does this for $attach support and not stepping into the REPL).
-DONT_DEBUG = [path.normcase(__file__), path.normcase(_vspu.__file__)]
+DONT_DEBUG = [
+    path.normcase(__file__),
+    path.normcase(ptvsd.__file__),
+    path.normcase(_vspu.__file__),
+    path.normcase(_vspr.__file__),
+    path.normcase(_vsipc.__file__),
+]
 if sys.version_info >= (3, 3):
     DONT_DEBUG.append(path.normcase('<frozen importlib._bootstrap>'))
 if sys.version_info >= (3, 5):
['Python/Product/PythonTools/ptvsd/debugger.py', 'Python/Product/PythonTools/ptvsd/attach_server.py']