perf script python: Add support for sqlite3 to call-graph-from-sql.py

perf script python: Add support for sqlite3 to call-graph-from-sql.py

Add support for SQLite 3 to the call-graph-from-sql.py script. The SQL
statements work as is, so just detect the database type by checking if the
SQLite 3 file exists.

Committer notes:

Tested collecting the PT data on a RHEL7.4, generating the SQLite3
database there and then moving it to a Fedora 26 system where the
call-graph-from-sql.py script was run, using python-pyside version
1.2.2-7fc26 to see the callgraphs using Qt4.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Link: http://lkml.kernel.org/r/1501749090-20357-6-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>