Fail early if configuration module can not initialize properly

In the case that the config module cannot load the driver for libconfig
or yaml, currently, there might be a cascade of errors that are
difficult for users to understand. For instance (partially redacted for
clarity):

    [CONFIG] Error calling dlopen(libparams_libconfig.so): libparams_libconfig.so: cannot open shared object file: No such file or directory
    [CONFIG] config module "libconfig" couldn't be loaded
    [CONFIG] config_get, section log_config skipped, config module not properly initialized
    [LOG] init aborted, configuration couldn't be performed
    [CONFIG] config_get, section (null) skipped, config module not properly initialized
    [CONFIG] /home/francesco/openairinterface5g/common/config/config_userapi.c 68 nfapi has no processed integer availablle
    [CONFIG] config_get, section (null) skipped, config module not properly initialized

    Assertion (get_softmodem_params()->default_pdu_session_id == -1) failed!
    In get_common_options() /home/francesco/openairinterface5g/executables/softmodem-common.c:161
    Use uicc0.pdu_sessions.[0].id to change the requested PDU session ID (is 0)

Here, the error is the missing shared object, but a user is more likely
to look at the last error instead of the first.

This commit addresses it by checking early for
CONFIG_ISFLAGSET(CONFIG_ABORT), and stopping if it is set. Additionally
changes include making functions static, removing late
CONFIG_ISFLAGSET() checks, and the CONFIG_ISFLAGSET() in
load_configmodule(), because at that time "uniqCfg" is not set yet and
thus does not do anything (this is likely a regression of an earlier
cleanup).

See-also: f50d5f5a9b ("make multiple config instead of one implicit
  global")

executables/nr-softmodem.c

@@ -514,7 +514,7 @@ int main( int argc, char **argv ) {
   start_background_system();
 
   ///static configuration for NR at the moment
-  if ((uniqCfg = load_configmodule(argc, argv, CONFIG_ENABLECMDLINEONLY)) == NULL) {
+  if ((uniqCfg = load_configmodule(argc, argv, CONFIG_ENABLECMDLINEONLY)) == NULL || CONFIG_ISFLAGSET(CONFIG_ABORT)) {
     exit_fun("[SOFTMODEM] Error, configuration module init failed\n");
   }
 
@@ -528,11 +528,6 @@ int main( int argc, char **argv ) {
   lock_memory_to_ram();
   get_options(uniqCfg);
 
-  if (CONFIG_ISFLAGSET(CONFIG_ABORT) ) {
-    fprintf(stderr,"Getting configuration failed\n");
-    exit(-1);
-  }
-
   if (!has_cap_sys_nice())
     LOG_W(UTIL,
           "no SYS_NICE capability: cannot set thread priority and affinity, consider running with sudo for optimum performance\n");

executables/nr-uesoftmodem.c

@@ -248,7 +248,7 @@ int main(int argc, char **argv)
 {
   start_background_system();
 
-  if ((uniqCfg = load_configmodule(argc, argv, CONFIG_ENABLECMDLINEONLY)) == NULL) {
+  if ((uniqCfg = load_configmodule(argc, argv, CONFIG_ENABLECMDLINEONLY)) == NULL || CONFIG_ISFLAGSET(CONFIG_ABORT)) {
     exit_fun("[SOFTMODEM] Error, configuration module init failed\n");
   }
   //set_softmodem_sighandler();