Ubuntu/Debian packages: Add conflict to libapache2-mod-php5filter

[ghost]

libapache2-mod-php5filter is known to block certain WebDAV/HTTP Verbs and causing various other issues like seen in the past:

#9395, #8536, #2495, #510

Today we had another user at IRC which had installed this package. It would make sense to add a conflict or similar to the ownCloud packages so that people are forced to install libapache2-mod-php5 instead to avoid such issues.

[nickvergessen]

@LukasReschke ?

[LukasReschke]

@jnweiger

[crrodriguez]

Already fixed

[ghost]

This wasn't fixed so created owncloud/administration#133 to address this issue