bitbake: Fix default function parameter assignment to a list

With python you should not assign a list as the default value of a
function parameter - because a list is mutable, the result will be that
the first time a value is passed it will actually modify the default.
Reference:

http://docs.python-guide.org/en/latest/writing/gotchas/#mutable-default-arguments

(Bitbake rev: 7859f7388f2e3f675d0e1527cfde18625f36f637)

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/toaster/toastergui/views.py

@@ -522,7 +522,9 @@ def builddashboard( request, build_id ):
 
 
 
-def generateCoveredList2( revlist = [] ):
+def generateCoveredList2( revlist = None ):
+    if not revlist:
+        revlist = []
     covered_list =  [ x for x in revlist if x.outcome == Task.OUTCOME_COVERED ]
     while len(covered_list):
         revlist =  [ x for x in revlist if x.outcome != Task.OUTCOME_COVERED ]