elm_config: Add fallback path to support lazy mount

elm_config: Add fallback path to support lazy mount

elm_config would access to user home directory to save their
config information. However, elm_config couldn't accesss to
the path because user data area could not be mounted
(Lazy mount of user data area[below /opt/usr/] is applied)

elm_config monitors some file which is created after mounting
then if it doesn't exist, elm_config will access to the other path

@tizen_feature

Change-Id: I5c43b1076ee0468bed8c6b443a8d02c03e0fe1f3
Signed-off-by: Wonki Kim <wonki_.kim@samsung.com>