community/clamav: fix clamd.conf

New release of clamav has changed $srcdir/etc/clamd.conf.sample such that there are now two commented out LocalSocket example lines. This causes the sed in APKBUILD's package function to uncomment both. This causes the clamd.initd start_pre functiion to emit a two line value for the local var socket, in turn, causing the evaluation of socketdir=${socket%/*} to be the whole first line. Now, when clamd.initd's start_pre check_path of $socketdir runs, it creates /run/clamav/clamd.sock as a directory, and now the start function cannot remove it.

This replaces the sed statements in package() function with a patch. Using a patch for this seems appropriate to me because the patch can be adjusted at later upgrades, but the sed statements can do unexpected things when the target file changes.