perf scripts python: exported-sql-viewer.py: Use new 'has_calls' column

If the new 'has_calls' column is present, use it with the call graph and
call tree to select only comms that have calls.

Committer testing:

Just started the exported-sql-view.py and accessed all the reports, no
backtraces.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/20190710085810.1650-17-adrian.hunter@intel.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>