selftests/bpf: close the file descriptor to avoid resource leaks

Static Analyis for bench_htab_mem.c with cppcheck:error
tools/testing/selftests/bpf/benchs/bench_htab_mem.c:284:3:
error: Resource leak: fd [resourceLeak]
tools/testing/selftests/bpf/prog_tests/sk_assign.c:41:3:
error: Resource leak: tc [resourceLeak]

fix the issue  by closing the file descriptor (fd & tc) when
read & fgets operation fails.

Signed-off-by: Malaya Kumar Rout <malayarout91@gmail.com>
Acked-by: Hou Tao <houtao1@huawei.com>

Author: malayarout91

tools/testing/selftests/bpf/benchs/bench_htab_mem.c

@@ -281,6 +281,7 @@ static void htab_mem_read_mem_cgrp_file(const char *name, unsigned long *value)
 	got = read(fd, buf, sizeof(buf) - 1);
 	if (got <= 0) {
 		*value = 0;
+		close(fd);
 		return;
 	}
 	buf[got] = 0;

tools/testing/selftests/bpf/prog_tests/sk_assign.c

@@ -37,8 +37,10 @@ configure_stack(void)
 	tc = popen("tc -V", "r");
 	if (CHECK_FAIL(!tc))
 		return false;
-	if (CHECK_FAIL(!fgets(tc_version, sizeof(tc_version), tc)))
+	if (CHECK_FAIL(!fgets(tc_version, sizeof(tc_version), tc))) {
+		pclose(tc);
 		return false;
+	}
 	if (strstr(tc_version, ", libbpf "))
 		prog = "test_sk_assign_libbpf.bpf.o";
 	else