Add basic libcynara-agent tests

Add basic tests for libcynara-admin library:
* tcag01_set_agent_type_policy_without_plugin - check if setting
 a policy with policy type provided by not loaded plugin fails;
* tcag02_set_agent_type_policy_with_plugin_loaded - checks if
 setting policy with policy type provided by loaded plugin succeeds;
* tcag03_check_with_no_agent - run cynara check that causes usage
 of plugin needing agent (but agent is not running) and verify
 that check returns DENY;
* tcag04_agent_initialize - check initialization and deinitialization
 og agent;
* tcag05_agent_request_timeout - run agent and register it in cynara
 service, break connection by resetting cynara after timeout;
* tcag06_check_with_unregistered_agent - run cynara check that causes
 usage of plugin needing agent (agent is running but not registered)
 and verify that chack returns DENY;
* tcag07_get_request - run simplest complete agent usage scenario:
    > agent registers in cynara,
    > a check using plugin and agent is done,
    > test acts as agent receiving and verifying request,
    > an ALLOW response is sent to cynara,
    > client receives proper ALLOW answer.

Change-Id: I781e9bb88b8686334acca4f9cf2c13a13bd643d5