elog-gen.py: Support subdirs

Add ability for elog-gen.py to find yaml files under subdirectories
so that yaml files found in Error/Callout/ and Error/IIC/ for
example can be found by the caller just passing the Error/ directory.

Change-Id: I91dcd523d2a75deea6266a3ea6885b88cd788206
Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>
diff --git a/tools/elog-gen.py b/tools/elog-gen.py
index 168e1fd..fe4807e 100755
--- a/tools/elog-gen.py
+++ b/tools/elog-gen.py
@@ -57,9 +57,10 @@
 
 
 def get_error_yaml_files(i_yaml_dir):
-    yaml_files = filter(
-        lambda file: file.endswith('.errors.yaml'),
-        os.listdir(i_yaml_dir))
+    yaml_files = []
+    for root, dirs, files in os.walk(i_yaml_dir):
+        for files in filter(lambda file: file.endswith('.errors.yaml'), files):
+            yaml_files.append(os.path.join(root, files))
     return yaml_files
 
 
@@ -110,7 +111,6 @@
 
     for error_yaml in error_yamls:
         # Verify the error yaml file
-        error_yaml = "/".join((i_yaml_dir, error_yaml))
         if (not (os.path.isfile(error_yaml))):
             print("Can not find input yaml file " + error_yaml)
             exit(1)