run-tests: move install.err into test area
Without this, sometimes installerrs generated errors
about no such file. It also did not work well when you
had multiple tests runners running around.
It also did not make sense to pollute the repository test
directory with the log file.
https://bz.mercurial-scm.org/1089
$ hg init
$ mkdir a
$ echo a > a/b
$ hg ci -Am m
adding a/b
$ hg rm a
removing a/b (glob)
$ hg ci -m m a
$ mkdir a b
$ echo a > a/b
$ hg ci -Am m
adding a/b
$ hg rm a
removing a/b (glob)
$ cd b
Relative delete:
$ hg ci -m m ../a
$ cd ..