tang: Fix installation error, missing fi statement

tang: Fix installation error, missing fi statement

root@OpenWrt:/# opkg install tang
Package tang (10-3) installed in root is up to date.
Configuring tang.
//usr/lib/opkg/info/tang.postinst: /usr/lib/opkg/info/tang.postinst-pkg: line 9: syntax error: unexpected end of file (expecting "fi")
Collected errors:
 * pkg_run_script: package "tang" postinst script returned status 2.
 * opkg_configure: tang.postinst returned 2.

Fix commit d49c79b76b7c7659e063290d1bc7d7fad626780a tang: remove outdated
 key handling.

if statement is not closed.

Signed-off-by: René van Dorst <opensource@vdorst.com>