Match RHEL Beta release strings

RHEL7 (in beta) has "Beta" after the release number and before the
code-name.  Add a number-match to the regex so everything between that
match and the codename in parenthesis is considered the release.

Change-Id: I992f20eedcefc6aeed6bd3ad57fc4cf20c8ef15d
Merge "Match RHEL Beta release strings"