Add deep copy of propq field in mac_dupctx to avoid double free

Add deep copy of propq field in mac_dupctx to avoid double free

mac_dupctx() should make a copy of the propq field. Currently it
does a shallow copy which can result in a double free and crash.
The double free occurs when using a provider property string.
For example, passing in "fips=no" to SSL_CTX_new_ex() causes the
propq field to get set to that value. When mac_dupctx() and
mac_freectx() is called (ie: in SSL_write()) it ends up freeing
the reference of the original object instead of a copy.

Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Shane Lontis <shane.lontis@oracle.com>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/13926)