test/telemetry: fix error handling for socket

test/telemetry: fix error handling for socket

When the socket connection failed, an error was printed to screen but
the function did not return an error, and continued to try read from the
socket. This is now corrected to close the socket and return -1 when the
connection fails.

Fixes: bd78cf693ebd ("test/telemetry: add unit tests for data to JSON")

Signed-off-by: Ciara Power <ciara.power@intel.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>