perf scripts python: exported-sql-viewer.py: Fix python3 support

perf scripts python: exported-sql-viewer.py: Fix python3 support

Unlike python2, python3 strings are not compatible with byte strings.
That results in disassembly not working for the branches reports. Fixup
those places overlooked in the port to python3.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Fixes: f25b3e4c823a ("perf script python: Add Python3 support to exported-sql-viewer.py")
Link: http://lkml.kernel.org/r/20190327072826.19168-3-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>