log: fix parsing of multiple trace:PATTERN log args

log: fix parsing of multiple trace:PATTERN log args

If giving QEMU a log arg which asks to enable multiple
different trace event patterns such as

  $QEMU -d trace:qio*,trace:qcrypto*

the parser will then invoke

  trace_enable_events("qio*,trace:qcrypto*")
  trace_enable_events("qcrypto*")

as when finding a 'trace:' prefix, it is not clever
enough to strip anything after the next comma. As
a result only the last 'trace:' match ever works.

Rather than trying to be more clever with parsing the
command line arg in place, simplify the code by
using g_strsplit to break it into individual strings
on ','. These resulting pieces can be directly used
without worrying about trailing data from the next
option.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Message-Id: <1473186343-16704-1-git-send-email-berrange@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>