rbd: don't link with -lcrypto

rbd support tries to both link with -lrados and -lcrypto. While the
first one is of course necessary, the second is not necessary (only
librados ifself needs to link with libcrypto).

This fixes a licensing issue: qemu as a whole is GPL v2, and thus can't
be linked with OpenSSL without an exception in the license, which seems
difficult to get given the number of persons involved.

Cc: Christian Brunner <chb@muc.de>
Signed-off-by: NAurelien Jarno <aurelien@aurel32.net>

configure

@@ -1802,7 +1802,7 @@ if test "$rbd" != "no" ; then
 #include <rados/librados.h>
 int main(void) { rados_initialize(0, NULL); return 0; }
 EOF
-  rbd_libs="-lrados -lcrypto"
+  rbd_libs="-lrados"
   if compile_prog "" "$rbd_libs" ; then
     librados_too_old=no
     cat > $TMPC <<EOF