Correct exception output for subnet deletion when port is used

Fixes bug 1093754

Change-Id: I2deaced0cfc2524234ff79e39e6e7c2f757ff19f
Ensure allocation pools are deleted from database

Fixes bug 1091946

Change-Id: I4330f7a81e4745d5885d58fe7c8a010d18a8e004
Exceptions cleanup

Ensure that the quantum exceptions in FAULT_MAP are grouped
together (this will save endless bug fixes when the server
will return 500 instead of 4xx)

Change-Id: I89581e1b6b4af3eb1803d6226686adf0b576d1e7
Merge "Exceptions cleanup"
Merge "Correct exception output for subnet deletion when port is used"
Merge "Ensure allocation pools are deleted from database"