[SMS] avoid mktime on NULL

gmtime(NULL) returns NULL at least in glibc and *can not* be used as
time(NULL). Since we compare two time_t values when checking the validity
period this can be replaced by time(NULL)
1 file changed
tree: 88b38f3ad50f69b21013c401489ac55d44f6f3ad
  1. hlrsync/
  2. linux-kernel/
  3. openbsc/
  4. wireshark/