gatt: Fix scan-build warnings

gatt: Fix scan-build warnings

This fixes the following warnings:

src/gatt-database.c:3541:14: warning: Value stored to 'iface' during
its initialization is never read [deadcode.DeadStores]
        const char *iface = g_dbus_proxy_get_interface(proxy);
                    ^~~~~   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
src/gatt-database.c:3542:14: warning: Value stored to 'path' during
its initialization is never read [deadcode.DeadStores]
        const char *path = g_dbus_proxy_get_path(proxy);
                    ^~~~   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Manika Shrivastava <manika.sh@samsung.com>
Signed-off-by: Ayush Garg <ayush.garg@samsung.com>