change discretize value to fix issues

Discretize of 0.0001 is okay for inches, but for metric <1microns would be quite small, this fixes some issues when generating paths for curves that look inward.
I found following post in the forum: https://forum.freecadweb.org/viewtopic.php?f=15&t=42755
I have experienced similar issues with other curves in my object.

src/Mod/Path/PathScripts/PathAdaptive.py

@@ -33,6 +33,7 @@ import json
 import math
 import area
 
+from FreeCAD import Units
 from PySide import QtCore
 
 # lazily loaded modules
@@ -104,7 +105,13 @@ def sceneClean():
 
 
 def discretize(edge, flipDirection=False):
-    pts = edge.discretize(Deflection=0.0001)
+    val=Units.Quantity("1mm").getUserPreferred()
+    if len(val)==3 and val[2]=='mm':
+        deflection=0.002
+    else:
+        deflection=0.0001
+
+    pts = edge.discretize(Deflection=deflection)
     if flipDirection:
         pts.reverse()