Retrieves metadata value of type timestamp.
     #include <time.h>
     hcerr_t hc_nvr_get_timestamp(hc_nvr_t *nvr, 
          hc_string_t name,
          struct timespec *value);
This function retrieves the value of type struct timespec associated with an indicated attribute name in a name-value record.
nvr
Points to a name-value-record.
name
IN: Name for the tuple.
value
OUT: Updated with the struct timespec (time.h) value.
     HCERR_OK
     HCERR_BAD_REQUEST
     HCERR_OOM
     HCERR_INVALID_NVR
     HCERR_ILLEGAL_ARGUMENT
     HCERR_ILLEGAL_VALUE_FOR_METADATA
     HCERR_NO_SUCH_ATTRIBUTE