sync_manager: Add callback to do rsync

Call rsync when the subscribed file or directory is modified or
deleted. Don't create error logs as syncing is used for backup
and does not affect the system's operation. Any errors will be
logged into the journal.

Closes openbmc/openbmc#2918

Change-Id: I2671f0afd2924c15ea883d4d037c641c6e9680b4
Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>
diff --git a/configure.ac b/configure.ac
index 1155cfe..0165e08 100755
--- a/configure.ac
+++ b/configure.ac
@@ -96,6 +96,8 @@
     [The base dir where all RO partitions are mounted])
 AC_DEFINE(BMC_ROFS_PREFIX, "/media/rofs-",
     [The prefix path for the versioned read-only bmc partitions])
+AC_DEFINE(ALT_RWFS, "/media/alt/var/persist",
+    [The path of the alt rwfs overlay])
 AC_DEFINE(PERSIST_DIR, "/var/lib/obmc/phosphor-bmc-code-mgmt/",
     [The dir where activation data is stored in files])
 AC_DEFINE(SYSTEMD_BUSNAME, "org.freedesktop.systemd1",