Support name change in devstack to debs

A short time ago, devstack change the name of its lists of debian
packages from apts to debs. In order to properly pre-cache, we should
read these.

Change-Id: Id784e2876a2cbbede650b7e101ff90f7d74ec367

nodepool/elements/cache-devstack/extra-data.d/55-cache-devstack-repos

@@ -134,7 +134,9 @@ def local_prep(distribution):
 
         if os.path.exists(os.path.join(TMP_MOUNT_PATH, 'usr/bin/apt-get')):
             debs = []
-            debdir = os.path.join(DEVSTACK, 'files', 'apts')
+            debdir = os.path.join(DEVSTACK, 'files', 'debs')
+            if not os.path.exists(debdir):
+                debdir = os.path.join(DEVSTACK, 'files', 'apts')
             for fn in os.listdir(debdir):
                 fn = os.path.join(debdir, fn)
                 tokenize(fn, debs, distribution, comment='#')

nodepool/scripts/cache_devstack.py

@@ -111,7 +111,9 @@ def local_prep(distribution):
 
         if os.path.exists('/usr/bin/apt-get'):
             debs = []
-            debdir = os.path.join(DEVSTACK, 'files', 'apts')
+            debdir = os.path.join(DEVSTACK, 'files', 'debs')
+            if not os.path.exists(debdir):
+                debdir = os.path.join(DEVSTACK, 'files', 'apts')
             for fn in os.listdir(debdir):
                 fn = os.path.join(debdir, fn)
                 tokenize(fn, debs, distribution, comment='#')