common_time: Fix a small build warning.

(cherry picked from commit f19c7a6)

> common_time: Fix a small build warning.
>
> Change-Id: I9a3652c8191ec86089117dbe6c16ff8612a911a3
> Signed-off-by: John Grossman <johngro@google.com>

Change-Id: I9d04f457d8a7f45249c86c4ad69bfd71fdd77245
Signed-off-by: John Grossman <johngro@google.com>

Author: johngro

services/common_time/common_time_server.cpp

@@ -584,7 +584,7 @@ bool CommonTimeServer::arbitrateMaster(
 
 static void hexDumpToString(const uint8_t* src, size_t src_len,
                             char* dst, size_t dst_len) {
-    size_t offset;
+    size_t offset = 0;
     size_t i;
 
     for (i = 0; (i < src_len) && (offset < dst_len); ++i) {