Build in tests/others/rpc folder was failing due to the use of LDFLAGS
variable instead of LDLIBS variable to link libprotobuf-c. The makefile
uses implicit build rules.

$(CC) $(LDFLAGS) n.o $(LOADLIBES) $(LDLIBS)

Using LDFLAGS places -llibprotobuf-c before the object files, preventing
the library from being searched for required functions.  This commit
changes the variable to LDLIBS instead to fix the issue.

travis-ci: success for test/others/rpc: fix build error
Signed-off-by: Venkateswara Rao Mandela <venkat.mandela@ti.com>
Reviewed-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>