Add new buildid cache if the update target file is not cached.

This can happen when an old binary is replaced by new one after caching
the old one. In this case, user sees his operation just failed.

But it does not look straight, since user just pass the binary "path",
not "build-id".

  ----
  # ./perf buildid-cache --add ./perf
  (update ./perf to new binary)
  # ./perf buildid-cache --update ./perf
  ./perf wasn't in the cache
  #
  ----

This patch adds given new binary to cache if the new binary is
not cached. So we'll not see the above error.

  ----
  # ./perf buildid-cache --add ./perf
  (update ./perf to new binary)
  # ./perf buildid-cache --update ./perf
  #
  ----
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Hemant Kumar <hemant@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20150226065440.23912.1494.stgit@localhost.localdomainSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>