Shorten instance ID to match restrictions.

Author: tseaver

system_tests/bigtable.py

@@ -37,7 +37,7 @@
 
 
 LOCATION_ID = 'us-central1-c'
-INSTANCE_ID = 'google-cloud' + unique_resource_id('-')
+INSTANCE_ID = 'g-c-p' + unique_resource_id('-')
 TABLE_ID = 'google-cloud-python-test-table'
 COLUMN_FAMILY_ID1 = u'col-fam-id1'
 COLUMN_FAMILY_ID2 = u'col-fam-id2'