resource: Support waiting for reserved resources until available

Before this patch, almost everything was in place to support concurrent
osmo-gsm-tester instances sharing a common state dir. However, during
resource reservation, if the reservation couldn't be done due to too
many resources being in use, osmo-gsm-tester would fail and skip the
test suite.
With this patch, OGT will wait until some reserved resources are
released and then try requesting the reservation again.

Change-Id: I938602ee890712fda82fd3f812d8edb1bcd05e08
diff --git a/doc/manuals/chapters/install.adoc b/doc/manuals/chapters/install.adoc
index 0e48e9d..c94c596 100644
--- a/doc/manuals/chapters/install.adoc
+++ b/doc/manuals/chapters/install.adoc
@@ -340,6 +340,7 @@
         python3-yaml \
         python3-mako \
         python3-gi \
+        python3-watchdog \
         locales
 ----