Fix multiple exporters panic (#1563)
Fix multiple exporters panic (#1563)

While using more than one exporter the panic runtime exception was fired
because the array allocated for exporters was as twice as big as it should

Signed-off-by: Dominik Rosiek <2ee6335924e387e2160d2cc1a287ed1d5b2c74c3@sumologic.com>
open-telemetry/opentelemetry-collector-contrib,open-telemetry/opentelemetry-collector,open-telemetry/opentelemetry-collector,open-telemetry/opentelemetry-collector-contrib,open-telemetry/opentelemetry-collector