recovery: reduce overall boot time

Move recovery-refresh and recovery-persist to onshot exec_background.
synchronous exec commands impact boot time.

Test: none
Bug: 65736247
Change-Id: Ic065c27b21f9bacbadee1e8c07bb15e2c41e0082

recovery-persist.rc

@@ -1,3 +1,3 @@
 on post-fs-data
     mkdir /data/misc/recovery 0770 system log
-    exec - system log -- /system/bin/recovery-persist
+    exec_background - system log -- /system/bin/recovery-persist

recovery-refresh.rc

@@ -1,2 +1,2 @@
 on post-fs
-    exec - system log -- /system/bin/recovery-refresh
+    exec_background - system log -- /system/bin/recovery-refresh