Update crash_reporter and metrics rc files to trigger on post-fs-data

The /data directory isn't guaranteed to be mounted during the
"on boot" trigger, so switch them to using "on post-fs-data".

Bug: 24941965
Change-Id: Iee84ca0e934967cff7bc4d968d9939d398c73980
diff --git a/crash_reporter.rc b/crash_reporter.rc
index 7bfe0c2..57c1d40 100644
--- a/crash_reporter.rc
+++ b/crash_reporter.rc
@@ -5,7 +5,7 @@
 on property:crash_reporter.coredump.enabled=0
     write /proc/sys/kernel/core_pattern "core"
 
-on boot
+on post-fs-data
     # Allow catching multiple unrelated concurrent crashes, but use a finite
     # number to prevent infinitely recursing on crash handling.
     write /proc/sys/kernel/core_pipe_limit 4