Bump the default timeout in dosep.py to 10m.

Summary:
This seems to be sufficient to get the tests taking longer than the
previous timeout of 5m to run to completion on Android to pass instead
of timing out.

Reviewers: chaoren

Reviewed By: chaoren

Subscribers: tberghammer, lldb-commits

Differential Revision: http://reviews.llvm.org/D9627

llvm-svn: 236913