mod_ladspa: Set setenv() overwrite flag to replace empty LADSPA_PATH variables.

For complete putenv()-like behaviour.

Further investigation on why putenv() caused EFAULTs on execve() and
segfaults on reload:

putenv(3):

   "The string pointed to by string becomes part of the environment,
    so altering the string changes the environment."

setenv(3):

   "This function makes copies of the strings pointed to by name and value
    (by contrast with putenv(3))."
Signed-off-by: Stefan Knoblich <s.knoblich@axsentis.de>

src/mod/applications/mod_ladspa/mod_ladspa.c

@@ -631,9 +631,9 @@ SWITCH_MODULE_LOAD_FUNCTION(mod_ladspa_load)
 
 	if (zstr(path)) {
 		if (switch_directory_exists("/usr/lib64/ladspa/", pool) == SWITCH_STATUS_SUCCESS) {
-			setenv("LADSPA_PATH", "/usr/lib64/ladspa/:/usr/local/lib/ladspa", 0);
+			setenv("LADSPA_PATH", "/usr/lib64/ladspa/:/usr/local/lib/ladspa", 1);
 		} else if (switch_directory_exists("/usr/lib/ladspa/", pool) == SWITCH_STATUS_SUCCESS) {
-			setenv("LADSPA_PATH", "/usr/lib/ladspa/:/usr/local/lib/ladspa", 0);
+			setenv("LADSPA_PATH", "/usr/lib/ladspa/:/usr/local/lib/ladspa", 1);
 		}
 	}