reinstate optional '(default)' suffix for 'module avail'

[boegel]

reinstate optional (default) suffix for module avail, since it's not stripped off with --terse in environment modules (it only is by lmod)

unit tests are enhanced to catch this problem should it occur again

[boegel]

The typical way of this bug being hit is when a module that is required as dependency is not seen by EasyBuild even though it is available, because it is marked as (default):

$ module av ictce
------------------------------------ /path/to/modules/all ------------------------------------
ictce/4.0.10      ictce/4.0.6      ictce/4.1.13(default)      ictce/5.1.1      ictce/5.3.0

$ eb gzip-1.5-ictce-4.1.13.eb
...
ERROR: EasyBuild crashed with an error (at easybuild/main.py:556 in resolve_dependencies):
Dependencies not met. Cannot resolve ["ictce/4.1.13 for {'dummy': True, 'toolchain':
{'version': 'dummy', 'name': 'dummy'}, 'name': 'ictce', 'versionsuffix': '',
'version': '4.1.13', 'parsed': True}"]

[stdweird]

what do you mean here?

[stdweird]

looks fine, please regtest

[boegel]

@stdweird: Thanks for the review, I'll merge this into develop and also in v1.8.x, and look into a full regtest for a v1.8.2 release of EasyBuild...