fix reading of string from file
fix reading of string from file

Reading the string from the trace file did not zero out the end
of the string. This caused funny characters to appear at the end
of the version listing.

Signed-off-by: Steven Rostedt <43232e92d70cc7aa53504ad0397085ee47bad87f@goodmis.org>

bigzz/trace-cmd,bigzz/trace-cmd