tests: Remove obsolete secaatest

tests: Remove obsolete secaatest

Before the security driver was refactored in d6623003 seclabeltest and
secaatest were basically the same. seclabeltest was meant for SELinux
and secaatest for AppArmor. Both tests exited early when the specific
security driver backend wasn't enabled.

With the new security manager trying to initialize a disabled security
driver backend is an error that can't be distinguished from other errors
anymore. Therefore, the updated seclabeltest just asks for the first
available backend as this will always work even with SELinux and AppArmor
backend being disabled due to the new Nop backend.

Remove the obsolete secaatest and compile and run the seclabeltest
unconditional.

This fixes make check on systems that support AppArmor.