This patch adds function are_values_in_array() to common test code. And
there is tc_are_values_in_array macro defined which is usefull for
talloc allocated values and arrays.

Resolves:
https://fedorahosted.org/sssd/ticket/2730

Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>

The function test_dom_suite_setup is a simple function which creates
a directory which should be used for creating files. This function
needn't be linked with libsss_util.so as other functions in common_dom.c
This is a reason why it's better to move it to the file common.c
so linker can optimize out other unnecessary module objects from static
library libsss_test_common.a and test needn't be linked libsss_util.so.

Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>

If configure isn't being run with argument --with-test-dir, then variable
TEST_DIR will be defined, but its value will be empty (""). In this case
opendir will fail with uncatched error "Directory does not exist, or name is
an empty string". Finally function call dirfd will segfault because its
argument is NULL.

I changed default value of TEST_DIR (if --with-test-dir was not used).

Function tests_set_cwd does not ignore return value of chdir, because
TEST_DIR should not be the empty string.

Print warning if sysdb-tests or sysdb-ssh test are run
individually and LDB_MODULES_PATH was not set.

https://fedorahosted.org/sssd/ticket/1820

tests/common.c is now required by all tests (check-based and not),
so we need to properly ifdef it

All 'make check' tests will chdir() into this directory before
running the suite. This provides the option of having temporary
files generated in a tmpfs or ramdisk

Also update BUILD.txt