NFS check configuration files.

Files are named NN.RPCSERVICE.check.  Files without a .check suffix
are ignored.

Supported variables are:

* family             - "tcp" or "udp" or space separated list
                       default: tcp, not used with "service_check_cmd"
* version            - optional, RPC service version number
                       default is to omit to check for any version,
                       not used with "service_check_cmd"
* unhealthy_after    - number of check fails before unhealthy
                       default: 1
* restart_every      - number of check fails before restart
                       default: 0, meaning no restart
* service_stop_cmd   - command to stop service
                       default: no default, must be provided if
                                restart_every > 0
* service_start_cmd  - command to start service
                       default: no default, must be provided if
                                restart_every > 0
* service_check_cmd  - command to check health of service
                       default is to check RPC service using rpcinfo
* service_debug_cmd  - command to debug a service after trying to stop it;
                       for example, it can be useful to print stack
                       traces of threads that have not exited, since
                       they may be stuck doing I/O;
                       no default, see also function program_stack_traces()

Quoting inside values is not preserved.
