(PUP-11897) Simplifyy wait_flags setting

This change simplifies the setting of wait_flags; the `0` is simpler
to look up in the table of valid flags in the ruby docs.

Author: tvpartytonight

lib/puppet/util/execution.rb

@@ -238,7 +238,7 @@ def self.execute(command, options = NoOptionsSpecified)
                 output << reader.read_nonblock(4096) if ready
               rescue Errno::EAGAIN
               rescue EOFError
-                wait_flags &= ~Process::WNOHANG
+                wait_flags = 0
               end
             end