liblog: don't bother keeping FD around once it's mapped.

Posix and linux explicitly state that this isn't necessary.

bug: 30963384
Change-Id: I2cc16ded04f0ebc909dc3027e02867594fb49d05
diff --git a/liblog/event_tag_map.c b/liblog/event_tag_map.c
index 3cb04cf..345f0d3 100644
--- a/liblog/event_tag_map.c
+++ b/liblog/event_tag_map.c
@@ -99,6 +99,9 @@
     if (processFile(newTagMap) != 0)
         goto fail;
 
+    if (fd >= 0)
+      close(fd);
+
     return newTagMap;
 
 fail: