Refactor samba antivirus

The zavs VFS plugin had two problems, huge memmory usage and huge
server overload because the scanner was loaded in each connection.

The new architecture has two parts. A VFS plugin (modified version
of scannedonly) sends to a socket (/var/lib/zentyal/zavs) the files
to scan, one in each line, with this format:
    user0x1Eaddr0x1Efile\n
    user - The user who access to the file
    addr - IP address of the client machine
    file - Absolute path of the file to scan
The fields are delimited by the non-printable ASCII char 0x1E.

A new daemon, zavsd creates this socket and listen on it. It has
a pool of threads locked in a queue where the main thread puts the
files to scan.
This new daemon is fully integrated with Zentyal framework and has
its own log file, /var/log/zentyal/zavsd.log
Remove duplicated slash
Add new dependence
Add missing antivirus configurating key
Grant access to 'ebox' user on shares and fix zavsd thread number config key
 When a user extensions modification is attempted, check  extension number before removing any data from LDAP
extracted method _checkUserExtensionNumber
added FirewallLogHelper.t
Create user journal directory in correct path
typo fix
Recover better of no-usercorner journal error in slave-sync
migration for versions with incorrect path
Disable IPv6
better changelog entry
Removed redundant cache_log line from squid4-external configuration
Merge pull request #127 from Zentyal/scabrero/disable-ipv6

Disable IPv6
Merge pull request #124 from Zentyal/jag/asterisk-modify-extension

 When a user extensions modification is attempted, check  extension numb...
Merge pull request #125 from Zentyal/jag/firewall-loghelper-test

added FirewallLogHelper.t
Merge pull request #126 from Zentyal/jag/usercorner-slavesync

Fixed master/slave usercorner sync
fixed typo