Create separate vardirs during collections test runs.

mysql-test/collections/default.daily

-perl mysql-test-run.pl --timer --force --comment=rpl_ndb_row --suite=rpl_ndb,ndb --mysqld=--binlog-format=row --experimental=collections/default.experimental
+perl mysql-test-run.pl --timer --force --comment=rpl_ndb_row --vardir=var-rpl_ndb_row --suite=rpl_ndb,ndb --mysqld=--binlog-format=row --experimental=collections/default.experimental

mysql-test/collections/default.push

-perl mysql-test-run.pl --timer --force --parallel=auto --comment=n_mix --mysqld=--binlog-format=mixed --experimental=collections/default.experimental
-perl mysql-test-run.pl --timer --force --parallel=auto --comment=ps_row --ps-protocol --mysqld=--binlog-format=row --experimental=collections/default.experimental
-perl mysql-test-run.pl --timer --force --parallel=auto --comment=embedded --embedded --experimental=collections/default.experimental
-perl mysql-test-run.pl --timer --force --parallel=auto --comment=rpl_binlog_row --suite=rpl,binlog --mysqld=--binlog-format=row --experimental=collections/default.experimental
-perl mysql-test-run.pl --timer --force --parallel=auto --comment=funcs_1 --suite=funcs_1 --experimental=collections/default.experimental
+perl mysql-test-run.pl --timer --force --parallel=auto --comment=n_mix --vardir=var-n_mix --mysqld=--binlog-format=mixed --experimental=collections/default.experimental
+perl mysql-test-run.pl --timer --force --parallel=auto --comment=ps_row --vardir=var-ps_row --ps-protocol --mysqld=--binlog-format=row --experimental=collections/default.experimental
+perl mysql-test-run.pl --timer --force --parallel=auto --comment=embedded --vardir=var-emebbed  --embedded --experimental=collections/default.experimental
+perl mysql-test-run.pl --timer --force --parallel=auto --comment=rpl_binlog_row --vardir=var-rpl_binlog_row  --suite=rpl,binlog --mysqld=--binlog-format=row --experimental=collections/default.experimental
+perl mysql-test-run.pl --timer --force --parallel=auto --comment=funcs_1 --vardir=var-funcs_1 --suite=funcs_1 --experimental=collections/default.experimental