image.py: rename _write_env -> _write_wic_env

Renamed this function as it's too generic name for it.
It writes variables, which are used by wic to .env file,
so _write_wic_env is better name for it.

Thanks Christopher Larson for poining out to this.

(From OE-Core rev: f8c7542164ebbe29613532c93ddc34c94238453c)

Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/lib/oe/image.py

@@ -326,7 +326,7 @@ class Image(ImageDepGraph):
 
         return image_cmd_groups
 
-    def _write_env(self):
+    def _write_wic_env(self):
         """
         Write environment variables used by wic
         to tmp/sysroots/<machine>/imgdata/<image>.env
@@ -353,7 +353,7 @@ class Image(ImageDepGraph):
 
         image_cmd_groups = self._get_imagecmds()
 
-        self._write_env()
+        self._write_wic_env()
 
         for image_cmds in image_cmd_groups:
             # create the images in parallel