Replace _exit(-1) with _exit(EXIT_FAILURE).

-1 is not a valid exit status.

Also replace a few exit(1) with exit(EXIT_FAILURE).

Test: mmma bootable/recovery
Change-Id: I4596c8328b770bf95acccc06a4401bd5cabd4bfd
diff --git a/updater/blockimg.cpp b/updater/blockimg.cpp
index 6755d78..03ce413 100644
--- a/updater/blockimg.cpp
+++ b/updater/blockimg.cpp
@@ -120,7 +120,7 @@
 
 err:
   LOG(ERROR) << "failed to parse range '" << range_text << "'";
-  exit(1);
+  exit(EXIT_FAILURE);
 }
 
 static bool range_overlaps(const RangeSet& r1, const RangeSet& r2) {