Bug 7446

When shared object which contains the symbols which cannot be resolved
is tried to be loaded twice by using dlopen with RTLD_NOW option,
first dlopen call fail (this is correct action), but second dlopen 
call succeed (this is illegal action).

Perhaps, when dlopen fail to resolve symbols, dlopen doesn't release
mmap and module handle, does it?

Fix: 

correct dlopen function.
How-To-Repeat: input follow files:
===========================
foo.c:
#include <stdio.h>
#include <stdlib.h>
#include <dlfcn.h>

int
main()
{
    void *h;
    
    if (NULL == (h=dlopen("var.so", RTLD_NOW))) {
        puts(dlerror());
    } else
        printf("success : %p\n", dlsym(h, "_var"));
    if (NULL == (h=dlopen("var.so", RTLD_NOW))) {
        puts(dlerror());
    } else
        printf("success : %p\n", dlsym(h, "_var"));
    return 0;
}
==============================
and var.c:
extern void hoge(void);

void var(void)
{
    hoge(); /* undefined symbol */
}
===============
And, compile and execute as follow:
% gcc -o foo foo.c
% gcc -c -fPIC var.c
% ld -Bshareable -o var.so var.o
% ./foo
Undefined symbol "_hoge" in foo:var.so
success : 0x2001b020
%