tests: add bootup tests

These are simple tests to check system that was just booted.

tests/test_bootup.py

+"""These are test that check that everything we need is running after boot. This does simple and quick tests to catch
+general errors such as disabled core services.
+"""
+import pytest
+
+
+def test_syslog_ng(client_board):
+    """Check that syslog-ng is running by checking if there is /var/log/messages (default log output).
+    """
+    client_board.run("[ -f /var/log/messages ]")
+
+
+@pytest.mark.parametrize("process", [
+    "crond",
+    "dnsmasq",
+    "kresd",
+    "lighttpd",
+    "mosquitto",
+    "netifd",
+    "odhcpd",
+    "rpcd",
+    "sshd",
+    "syslog-ng",
+    "ubusd",
+    "watchdog",
+
+])
+def test_processes(client_board, process):
+    """Check that various essential processes are running.
+    """
+    client_board.run("pgrep -x '{p}' || pgrep -x \"$(which '{p}')\"".format(p=process))
+
+
+def test_lighttpd(client_board):
+    """Test that there is access to router interface.
+    """
+    # TODO