Added a NETWORK trace tag. am: 785735bd

#define ATRACE_TAG_PACKAGE_MANAGER  (1<<18)

#define ATRACE_TAG_SYSTEM_SERVER    (1<<19)

#define ATRACE_TAG_DATABASE         (1<<20)

#define ATRACE_TAG_LAST             ATRACE_TAG_DATABASE

#define ATRACE_TAG_NETWORK          (1<<21)

#define ATRACE_TAG_LAST             ATRACE_TAG_NETWORK

// Reserved for initialization.

#define ATRACE_TAG_NOT_READY        (1ULL<<63)