Move apply_chunk_growth outside of a for-cycle
Move apply_chunk_growth outside of a for-cycle

Otherwise it is for no reason defined again and again. Prepend an underscore to
its name to mark it private.

Related: rhbz#1093144

jkonecny12/blivet,vpodzime/blivet,dwlehman/blivet,vpodzime/blivet,AdamWill/blivet,rvykydal/blivet,vojtechtrefny/blivet,dwlehman/blivet,rhinstaller/blivet,rvykydal/blivet,jkonecny12/blivet,vojtechtrefny/blivet,AdamWill/blivet,rhinstaller/blivet