master: Remove some remaining quota code

Commit b42150b24ca97180a52fdfcde19ace5aaa18cd2a "Remove the never
released MooseFS 1.7 quotas" left some unremoved quota code.

Remove it now.

Change-Id: I2f6adf990a3a8d1d94452ce076bdc1eb9c2c3e6e