tests: reduce length of nodeinfodata test names

Commit ddd6bef4 switched to the ustar format to fix an issue where
'make dist' fails to create a tarball because we have files with
relative names longer than 100 bytes by the time you include a
'libvirt-0.9.13' prefix.  Unfortunately, even with ustar format,
the use of 'tar -ch' tries to convert symlinks to hard links,
also with a name too long (omitting the -h works, but automake
automatically passes -h); such symlinks were added in commit
6dcf98c8, which resulted in 'make dist' breaking again.  The
solution is to rename the offending symlinks to something shorter,
by shortening the entire nodeinfodata naming scheme.

* tests/nodeinfotest.c (mymain): Shorten test names.
(linuxTestNodeInfo): Accommodate new names.
* tests/nodeinfodata/*: Rename files accordingly.