env: fix the env export varname

The env export command doesn't export the first variable of the list
since commit 5a31ea04c9
"env grep" - reimplement command using hexport_r()

Signed-off-by: Pierre Aubert <p.aubert@staubli.com>

lib/hashtable.c

@@ -564,7 +564,7 @@ static int match_entry(ENTRY *ep, int flag,
 	int arg;
 	void *priv = NULL;
 
-	for (arg = 1; arg < argc; ++arg) {
+	for (arg = 0; arg < argc; ++arg) {
 #ifdef CONFIG_REGEX
 		struct slre slre;