guess: return RH osdist for eng- dist-git branches

Red Hat's rel-eng team uses "eng-rhel-6" and "eng-rhel-7" branches in
dist-git. Return a product that begins with "RH" so that the "rdopkg
new-version" command will automatically upload new source tarballs to
the lookaside cache when operating here.

Change-Id: I65ae0183acd4633aba4e44aa4038ee81b6154197

Author: ktdreyer

rdopkg/guess.py

@@ -262,6 +262,8 @@ def osdist(branch=None):
         return 'RHCEPH'
     if branch.startswith('rhscon-'):
         return 'RHSCON'
+    if branch.startswith('eng-'):
+        return 'RHENG'
     # XXX Detect 'Fedora' here? From r'f\d+' branches possibly.
     return 'RDO'