Fix memory leak in RCconfig_nr_parallel

* strdup() function is returning a malloced string
  which must be freed after use
* replace the strdup with direct use of strings to avoid heap allocation

> Direct leak of 23 byte(s) in 1 object(s) allocated from:
    > 0 0x7ffff745b9a7 in __interceptor_strdup ../../../../src/libsanitizer/asan/asan_interceptors.cpp:454
    > 1 0x555559e36f87 in RCconfig_nr_parallel /openair2/GNB_APP/gnb_config.c:2054
    > 2 0x555559e38ea3 in NRRCConfig /openair2/GNB_APP/gnb_config.c:2097
    > 3 0x555559155542 in get_options /executables/nr-softmodem.c:423
    > 4 0x555559155542 in main /executables/nr-softmodem.c:623
    > 5 0x7ffff5e29d8f in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58

> Direct leak of 14 byte(s) in 1 object(s) allocated from:
    > 0 0x7ffff745b9a7 in __interceptor_strdup ../../../../src/libsanitizer/asan/asan_interceptors.cpp:454
    > 1 0x555559e370c5 in RCconfig_nr_parallel /openair2/GNB_APP/gnb_config.c:2063
    > 2 0x555559e38ea3 in NRRCConfig /openair2/GNB_APP/gnb_config.c:2097
    > 3 0x555559155542 in get_options /executables/nr-softmodem.c:423
    > 4 0x555559155542 in main /executables/nr-softmodem.c:623
    > 5 0x7ffff5e29d8f in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58

openair2/GNB_APP/gnb_config.c

@@ -2041,31 +2041,29 @@ int RCconfig_NR_NG(MessageDef *msg_p, uint32_t i) {
 }
 
 int RCconfig_nr_parallel(void) {
-  char *parallel_conf = NULL;
-  char *worker_conf   = NULL;
   extern char *parallel_config;
   extern char *worker_config;
   paramdef_t ThreadParams[]  = THREAD_CONF_DESC;
   paramlist_def_t THREADParamList = {THREAD_CONFIG_STRING_THREAD_STRUCT,NULL,0};
   config_getlist(config_get_if(), &THREADParamList, NULL, 0, NULL);
 
+  char *default_parallel_conf = "PARALLEL_RU_L1_TRX_SPLIT";
+  char *default_worker_conf = "WORKER_ENABLE";
+  char *parallel_conf = default_parallel_conf;
+  char *worker_conf = default_worker_conf;
+
   if(THREADParamList.numelt>0) {
     config_getlist(config_get_if(), &THREADParamList, ThreadParams, sizeofArray(ThreadParams), NULL);
-    parallel_conf = strdup(*(THREADParamList.paramarray[0][THREAD_PARALLEL_IDX].strptr));
-  } else {
-    parallel_conf = strdup("PARALLEL_RU_L1_TRX_SPLIT");
+    parallel_conf = *(THREADParamList.paramarray[0][THREAD_PARALLEL_IDX].strptr);
   }
 
   if(THREADParamList.numelt>0) {
     config_getlist(config_get_if(), &THREADParamList, ThreadParams, sizeofArray(ThreadParams), NULL);
-    worker_conf   = strdup(*(THREADParamList.paramarray[0][THREAD_WORKER_IDX].strptr));
-  } else {
-    worker_conf   = strdup("WORKER_ENABLE");
+    worker_conf = *(THREADParamList.paramarray[0][THREAD_WORKER_IDX].strptr);
   }
 
   if(parallel_config == NULL) set_parallel_conf(parallel_conf);
   if(worker_config == NULL)   set_worker_conf(worker_conf);
-
   return 0;
 }