1. Add a chdir context manager

2. Add a abs path joining function that will return the absolute path of
   a combined path (where applicable)

cloudinit/util.py

@@ -486,6 +486,16 @@ def mergedict(src, cand):
     return src
 
 
+@contextlib.contextmanager
+def chdir(ndir):
+    curr = os.getcwd()
+    try:
+        os.chdir(ndir)
+        yield ndir
+    finally:
+        os.chdir(curr)
+
+
 @contextlib.contextmanager
 def umask(n_msk):
     old = os.umask(n_msk)
@@ -1285,6 +1295,10 @@ def subp(args, data=None, rcs=None, env=None, capture=True, shell=False):
     return (out, err)
 
 
+def abs_join(*paths):
+    return os.path.abspath(os.path.join(*paths))
+
+
 # shellify, takes a list of commands
 #  for each entry in the list
 #    if it is an array, shell protect it (with single ticks)