Don't search off the end of the index for bad Olson ids.

In the old code, the index was a file to itself, so it made sense to
read until you hit the end of the file. In the new code, the index is
followed by hundreds of KiB of data, so we need to just search the
index.

Bug: 8368791
Change-Id: Icf5f8b5516cf3a93679fa849c9f6cd1cb100e0f1

tests/Android.mk

@@ -74,6 +74,7 @@ test_src_files = \
     string_test.cpp \
     strings_test.cpp \
     stubs_test.cpp \
+    time_test.cpp \
     unistd_test.cpp \
 
 test_dynamic_ldflags = -Wl,--export-dynamic -Wl,-u,DlSymTestFunction