test: Make testing work on systems without or old systemd

* Introduce a macro to conditionally execute tests. This avoids
  skipping the entire test if some parts require systemd
* Skip the journal tests when no /etc/machine-id is present
* Change test-catalog to load the catalog from the source directory
  of systemd.
* /proc/PID/comm got introduced in v2.6.33 but travis is still
  using v2.6.32.
* Enable make check and make distcheck on the travis build
* Use -D"CATALOG_DIR=STR($(abs_top_srcdir)/catalog)" as a STRINGIY
  would result in the path '/home/ich/source/linux' to be expanded
  to '/home/ich/source/1' as linux is defined to 1.
man: typo

ohsix> ooh theres a typo in the example
use CAP_MKNOD ConditionCapability

Fixes errors seen when booting VMs on QEMU like

systemd[1]: kmod-static-nodes.service: main process exited, code=exited, status=203/EXEC
systemd[1]: Failed to start Create list of required static device nodes for the current kernel.
systemd[1]: Unit kmod-static-nodes.service entered failed state.

Make sure that mknod capability is available

Signed-off-by: Khem Raj <raj.khem@gmail.com>
remove hasprefix(), use startswith()
Optimize startswith() to macro

I guess it's easier and cleaner anyway to use simple static inline
functions instead of defines.