avicii: Pin netmgr_config.xml

/bin/bash -c "(out/soong/host/linux-x86/bin/xmllint vendor/oneplus/avicii/proprietary/vendor/etc/data/netmgr_config.xml >/dev/null ) && (mkdir -p out/target/product/avicii/vendor/etc/data/ ) && (rm -f out/target/product/avicii/vendor/etc/data/netmgr_config.xml ) && (cp \"vendor/oneplus/avicii/proprietary/vendor/etc/data/netmgr_config.xml\" \"out/target/product/avicii/vendor/etc/data/netmgr_config.xml\" )"
vendor/oneplus/avicii/proprietary/vendor/etc/data/netmgr_config.xml:8: parser error : XML declaration allowed only at the start of the document
<?xml version="1.0" encoding="UTF-8"?>
     ^
vendor/oneplus/avicii/proprietary/vendor/etc/data/netmgr_config.xml:2874: parser error : Double hyphen within comment: <!-- richy.li@Connectivity, 2019/09/16, set tcp_mtu_pr
      <!-- #endif VENDOR_EDIT -->

Change-Id: Iadb0168c2113629c7b2a5ebe20bc88c6a2d77229