test/blobfs: set blobfs cache size when starting fuse

mkfs also uses 512MiB as the default cache size, so here
we also use 512MiB for fuse, or the fuse will allocate
4096MiB.

Fix issue #1309.

Change-Id: Icb4c3a175107bb56f4f84a0b0435d05f6f44f15e
Signed-off-by: Changpeng Liu <changpeng.liu@intel.com>
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/2112
Community-CI: Mellanox Build Bot
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Tomasz Zawadzki <tomasz.zawadzki@intel.com>
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>

test/blobfs/fuse/fuse.c

@@ -105,6 +105,8 @@ int main(int argc, char **argv)
 	g_fuse_argc = argc - 2;
 	g_fuse_argv = &argv[2];
 
+	spdk_fs_set_cache_size(512);
+
 	rc = spdk_app_start(&opts, spdk_fuse_run, NULL);
 	spdk_app_fini();