[lib][trusty] Destory uctx if exists

Syscall exit_etc invokes all available shutdown callbak of notifier in
application notifiers list. In this case, uctx teardwon would be

Add condition check before destroy uctx of application. With this
change, Trusty applicaiton could be created without uctx.

Bug: 119111590
Change-Id: I473186ec204ea808d790442f687bd262b9c56c2d
1 file changed