maint: split long lines in Makefiles

maint: split long lines in Makefiles

Makefiles are another easy file to enforce line limits.

Mostly straightforward; interesting tricks worth noting:
src/Makefile.am: $(confdir) was already defined, use it in more places
tests/Makefile.am: path_add and VG required some interesting compression

* cfg.mk (sc_prohibit_long_lines): Add another test.
* Makefile.am: Fix offenders.
* daemon/Makefile.am: Likewise.
* docs/Makefile.am: Likewise.
* python/Makefile.am: Likewise.
* src/Makefile.am: Likewise.
* tests/Makefile.am: Likewise.

Signed-off-by: Eric Blake <eblake@redhat.com>