virfilemock: Init symbols in canonicalize_file_name()

If a program that is using this mock calls canonicalize_file_name()
as the very first function then it will face SIGSEGV because
real_canonicalize_file_name is uninitialized.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>

tests/virfilemock.c

@@ -177,6 +177,9 @@ statfs(const char *path, struct statfs *buf)
 char *
 canonicalize_file_name(const char *path)
 {
+
+    init_syms();
+
     if (getenv("LIBVIRT_MTAB")) {
         const char *p;
         char *ret;