tests: Add a test case for testing --runas and ability to access files

tests: Add a test case for testing --runas and ability to access files

Add a test case for testing the --runas parameter and the ability to access
existing files that have restrictive access permission so that only allow
the --runas user is able to access these files. This is to ensure that
swtpm can access these files properly when the handling of options and the
changing to the --runas user is moved around within swtpm.

Skip the test case if swtpm is linked with ASAN since then we get these
types of error messages that fail tests:

==== Starting swtpm with interfaces socket+socket ====
==3303263==LeakSanitizer has encountered a fatal error.
==3303263==HINT: For debugging, try setting environment variable LSAN_OPTIONS=verbosity=1:log_threads=1
==3303263==HINT: LeakSanitizer does not work under ptrace (strace, gdb, etc)

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>