Close va_start with va_end in syslog.cc
Close va_start with va_end in syslog.cc

All va_start must be accompanied by a va_end even after the usage of
svnprintf.

PiperOrigin-RevId: 243120399
Change-Id: I592a499534a3ebaee36929f68fd0345fac91560f

google/asylo,google/asylo,google/asylo,google/asylo,google/asylo,google/asylo