bootstat: test: fix Its_Just_So_Hard_reboot

Add the test injection to known list, and deal with an error
propagation issue.

Test: system/core/bootstat/boot_reason_test.sh Its_Just_So_Hard_reboot
Bug: 63736262
Change-Id: I4799956978a8884c69c830fcedd7febd143651fd
diff --git a/bootstat/bootstat.cpp b/bootstat/bootstat.cpp
index c1d799e..2f9e7a7 100644
--- a/bootstat/bootstat.cpp
+++ b/bootstat/bootstat.cpp
@@ -225,6 +225,8 @@
     {"reboot,longkey", 85},
     {"reboot,2sec", 86},
     {"shutdown,thermal,battery", 87},
+    {"reboot,its_just_so_hard", 88},  // produced by boot_reason_test
+    {"reboot,Its Just So Hard", 89},  // produced by boot_reason_test
 };
 
 // Converts a string value representing the reason the system booted to an