Branch b1_6

Update build version to 1.6.6.50, since b_release_1_6_6 was branched already.

lustre/autoconf/lustre-version.ac

 m4_define([LUSTRE_MAJOR],[1])
 m4_define([LUSTRE_MINOR],[6])
-m4_define([LUSTRE_PATCH],[5])
-m4_define([LUSTRE_FIX],[52])
+m4_define([LUSTRE_PATCH],[6])
+m4_define([LUSTRE_FIX],[50])
 # Note: we're starting prerelease versions at 50 this time.
 
 dnl # don't forget to update the service tags info