fix to allow not using connstring parameter in pgsql plugin

commit a565216f3f772514356a067d68b775331b01832a

Author: Bob Hockney <[email protected]>
Date:   Sat Apr 19 12:43:37 2014 -0600

Connection parameters other than connstring are ignored, forcing its use. u.string in config_keyset in conffile.h is a character array, not a pointer, and is initialized as a zero length string, not a null pointer, so the pointer assignment to connstr will always be a valid pointer, not NULL, so (! connstr) will always be false.

index fda289e..ac87a64 100644
@@ -236,7 +236,7 @@ static int open_db_pgsql(struct ulogd_pluginstance *upi)
     char *schema = NULL;
     char pgbuf[128];
 
-    if (!connstr) {
+    if (! strlen(connstr)) {
         char *server = host_ce(upi->config_kset).u.string;
         unsigned int port = port_ce(upi->config_kset).u.value;
         char *user = user_ce(upi->config_kset).u.string;