net/inet and net/tcp: Fix tcp close flow; free the connection after all tcp close process finished.

sched/environ/env_getenv.c

@@ -81,7 +81,7 @@ FAR char *getenv(FAR const char *name)
 
   /* Verify that a string was passed */
 
-  if (!name)
+  if (name == NULL)
     {
       ret = EINVAL;
       goto errout;
@@ -95,7 +95,7 @@ FAR char *getenv(FAR const char *name)
 
   /* Check if the variable exists */
 
-  if (!group || (pvar = env_findvar(group, name)) == NULL)
+  if (group == NULL || (pvar = env_findvar(group, name)) == NULL)
     {
       ret = ENOENT;
       goto errout_with_lock;
@@ -104,7 +104,7 @@ FAR char *getenv(FAR const char *name)
   /* It does!  Get the value sub-string from the name=value string */
 
   pvalue = strchr(pvar, '=');
-  if (!pvalue)
+  if (pvalue == NULL)
     {
       /* The name=value string has no '='  This is a bug! */