perf trace: Fix summary_only option

perf trace: Fix summary_only option

The intent of the -s/--summary-only option is to just show a summary of
the system calls and statistics without any of the individual events.
Commit e596663ebb2 broke that by showing the interrupted lines:

perf trace -i perf.data -s
...
     0.741 ( 0.000 ms): sleep/31316 fstat(fd: 4, statbuf: 0x7ffc75ceb830                                  ) ...
     0.744 ( 0.000 ms): sleep/31316 mmap(len: 100244, prot: READ, flags: PRIVATE, fd: 4                   ) ...
     0.747 ( 0.000 ms): perf/31315 write(fd: 3, buf: 0x7d4bb0, count: 8                                  ) ...
...

Fix by checking for the summary only option.

Signed-off-by: David Ahern <dsahern@gmail.com>
Link: http://lkml.kernel.org/r/1426789383-19023-1-git-send-email-dsahern@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>