MEDIUM: Move {,fast,down}inter to struct check

Move {,fast,down}inter elements from struct server to struct check.
This allows those elements of a check to be independent of the check's server.
This is in preparation for adding a second struct check element to struct
server.

Signed-off-by: Simon Horman <horms@verge.net.au>
MEDIUM: Move result element to struct check

Move result element from struct server to struct check
This allows check results to be independent of the check's server.
This is in preparation for adding a second struct check element to struct
server.

Signed-off-by: Simon Horman <horms@verge.net.au>
MEDIUM: Paramatise functions over check

set_server_down
set_server_up
srv_getinter
server_status_printf
set_server_check_status
set_server_disabled
cfgparse; Factor out check initialisation

This is in preparation for struct server having two elements
of type struct check.
Add state to struct check

Add state to struct check. This is currently used to store one bit,
CHK_RUNNING, which is set if a check is running and clear otherwise.
This bit was previously SRV_CHK_RUNNING of the state element of struct
server. Moving it to struct check allows checks of the same server
to be run independently.

Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
check name
Move health element from struct server to struct check

This allows the health of checks of the same server to be
stored independently.

Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Add type type to struct check

This is used to indicate the type of a check. This is in preparation
for allowing a server to have more than one check by allowing checks
to have a type independent of their proxy's option2 settings. That is
to allow the types of a server's checks to differ.
Add helper for task creation for checks

This helper reduce code duplication when a secondary agent check
is added to servers.
Add agent to struct server