Fix broken variables tree iteration.

This fixes whole number of problems with iterating through RB tree
containing variables. Especially:
https://dev.cfengine.com/issues/6033
https://dev.cfengine.com/issues/6779

EvalContextVariableTableIteratorNew is calling VariableTableIteratorNew
which is not aware of variable indexes (VarRef->indices). Then while picking
value form tree to be iterator it might or might not contain indexes.
Randomly selecting variable with wrong index (and number of indexes)
is causing wrong behavior while iterating through list of variables.
VariableTableIteratorNext is checking indexes and returning variables
based on VariableTableIterator selected previously by
EvalContextVariableTableIteratorNew which is totally unreliable in case
of arrays.
Fix relaying on order of keys returned by maparray.
Disable problematic acceptance test completely on Solaris 11.
Fix fakeroot messing up a test by moving it to the unsafe area.

Fakeroot's file magic somehow interferes with the backgrounded
promises which in turn leads to stale processes lingering after the
test has finished.
readfile and textxform functions do not rely on 4k limit anymore
Added text_xform tests for large sizes
CF_INFINITY is not a limit for buffer size, it's just an indication that policy has the parameter 'inf'.
Comment for clarity.
A couple of TODOs.
metadata for story id 5525 and 5526 (user present and absent)

Modified by: Kristian Amlie <kristian.amlie@cfengine.com>
Merge pull request #2035 from pasinskim/redmine_6779

Fix broken variables tree iteration.