virmock: Initialize both symbols in VIR_MOCK_REAL_INIT_ALT

It may happen that both symbols are present. Especially when
chaining mocks. For instance if a test is using virpcimock and
then both stat and __xstat would be present in the address space
as virpcimock implements both. Then, if the test would try to use
say virfilewrapper (which again uses VIR_MOCK_REAL_INIT_ALT() to
init real_stat and real___xstat) it would find stat() from
virpcimock and stop there. The virfilewrapper.c:real___xstat
wouldn't be initialized and thus it may result in a segfault.

The reason for segfault is that sys/stat.h may redefine stat() to
call __xstat().
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>

tests/virmock.h

@@ -292,8 +292,9 @@
 
 # define VIR_MOCK_REAL_INIT_ALT(name1, name2) \
     do { \
-        if (!(real_ ## name1 = dlsym(RTLD_NEXT, #name1)) && \
-            !(real_ ## name2 = dlsym(RTLD_NEXT, #name2))) { \
+        real_ ## name1 = dlsym(RTLD_NEXT, #name1); \
+        real_ ## name2 = dlsym(RTLD_NEXT, #name2); \
+        if (!real_##name1 && !real_##name2) { \
             fprintf(stderr, "Cannot find real '%s' or '%s' symbol\n", \
                     #name1, #name2); \
             abort(); \