silence ovgetvar command logging

[Derek_]

Most of the commands now call log_command_usage() when run. For ovgetvar in particular, which is called frequently, this causes excessive logging.

[Derek_ (derek-name)]

Example of the logging:
            Dec 1 18:06:26 hostname ovgetvar[1229]: "/usr/bin/ovgetvar"" called with arguments: "open" "gtm_path"
            Dec 1 18:06:27 hostname ovgetvar[1270]: "/usr/bin/ovgetvar"" called with arguments: "open" "gtm_path"
            Dec 1 18:06:27 hostname ovgetvar[1321]: "/usr/bin/ovgetvar"" called with arguments: "open" "gtm_path"
            Dec 1 18:06:27 hostname ovgetvar[1363]: "/usr/bin/ovgetvar"" called with arguments: "open" "gtmgbldir"
            Dec 1 18:06:28 hostname ovgetvar[1420]: "/usr/bin/ovgetvar"" called with arguments: "open" "gtmroutines"

The frequent calls to ovgetvar come from the ZCD routine.

Additional logging noise comes due to LIST^ZCD calling ovgetvar on all files and directories in the OpenVista root directory, and using ovgetvar to test if each is an OpenVista instance. So, for example:

            Dec 1 18:01:06 hostname ovgetvar[22396]: "/usr/bin/ovgetvar"" called with arguments: "lost+found" "gtm_path"
            Dec 1 18:01:06 hostname ovgetvar[22396]: Could not set GT.M environment for instance "lost+found": /opt/openvista/lost+found has incorrect ownership or permissions