obj: add locking to the OBJ sigid calls
obj: add locking to the OBJ sigid calls

This is done using a single global lock.  The premise for this is that new
objects will most frequently be added at start up and never added subsequently.
Thus, the locking will be for read most of the time.

Reviewed-by: Tomas Mraz <2bc6038c3dfca09b2da23c8b6da8ba884dc2dcc2@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/15713)

openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl