stackrc: Make REQUIREMENTS_DIR configurable

In cases where global REQUIREMENTS_DIR is set, use it
instead of overwriting it. This is particularly needed
in cases where users of pip_install wrapper have the
upper-constraints.txt at another location.

Change-Id: I34e9f94548c575e1af5bca9655a3b7d1915375a8
Signed-off-by: Flavio Fernandes <flaviof@redhat.com>
1 file changed