LegacyGatewayRPCTest: fix memory leak
LegacyGatewayRPCTest: fix memory leak

Memory leak was caused by incorrect creation of RPCConnector and
LegacyGatewayRPC, that were shared among all subtests. Now, new RPC is
created for each subtest. This removed dependencies between subtests
also.

Reported-by: Jan Viktorin <3eab6ac54c005c4408f608556a6663b7f2abede7@fit.vutbr.cz>
Fixes:c9aac6bd9bb2 ("test: LegacyGatewayRPCTest")
Signed-off-by: Jozef Halaj <d60338334aa79f5c61824693142b417ad5db682f@stud.fit.vutbr.cz>
Acked-by: Jan Viktorin <3eab6ac54c005c4408f608556a6663b7f2abede7@fit.vutbr.cz>

BeeeOn/server,BeeeOn/server,BeeeOn/server,BeeeOn/server