REORG: server: Export and rename some functions updating server info

REORG: server: Export and rename some functions updating server info

Some static functions are now exported and renamed to follow the same
pattern of other exported functions. Here is the list :

 * update_server_fqdn: Renamed to srv_update_fqdn and exported
 * update_server_check_addr_port: renamed to srv_update_check_addr_port and exported
 * update_server_agent_addr_port: renamed to srv_update_agent_addr_port and exported
 * update_server_addr: renamed to srv_update_addr
 * update_server_addr_potr: renamed to srv_update_addr_port
 * srv_prepare_for_resolution: exported

This change is mandatory to move all functions dealing with the server-state
files in a separate file.