Stop init loops

Under certain circumstances, the libcrypto init code would loop,
causing a deadlock.  This would typically happen if something in
ossl_init_base() caused an OpenSSL error, and the error stack routines
would recurse into the init code before the flag that ossl_init_base()
had been run was checked.

This change makes sure ossl_init_base isn't run once more of the base
is initiated.

Thanks to Dmitry Kostjuchenko for the idea.

Fixes Github issue #1899

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1922)