epc: Drop signal(SIGKILL) calls

SIGKILL cannot be intercepted by apps, so it's useless adding a signal
handler for them. I'm pretty sure the signal() function is erroring in
this scenarios. From signal() man page:
"The signals SIGKILL and SIGSTOP cannot be caught or ignored."

srsepc/src/main.cc

@@ -384,7 +384,6 @@ int main(int argc, char* argv[])
 {
   signal(SIGINT, sig_int_handler);
   signal(SIGTERM, sig_int_handler);
-  signal(SIGKILL, sig_int_handler);
 
   // print build info
   cout << endl << get_build_string() << endl;

srsepc/src/mbms-gw/main.cc

@@ -190,7 +190,6 @@ int main(int argc, char* argv[])
   cout << endl << "---  Software Radio Systems MBMS  ---" << endl << endl;
   signal(SIGINT, sig_int_handler);
   signal(SIGTERM, sig_int_handler);
-  signal(SIGKILL, sig_int_handler);
 
   all_args_t args;
   parse_args(&args, argc, argv);