Refactor: libcrmcommon: Drop calls to gnutls_global_init()/deinit()

Except in deprecated crm_gnutls_global_init(). As of GnuTLS 3.3.0, the
GnuTLS library is initialized on load, and it's no longer necessary to
call these functions explicitly.

https://www.gnutls.org/manual/html_node/Initialization.html
https://www.gnutls.org/manual/html_node/Core-TLS-API.html#gnutls_005fglobal_005finit

Ref T967

Signed-off-by: Reid Wahl <nrwahl@protonmail.com>