Bug 919982: B2G RIL - Instantiate additional ril-daemon/rilproxy services.

Since [bug 814568](https://bugzilla.mozilla.org/show_bug.cgi?id=814568), we have 8 additional virtual modems in emulator.  They have been enabled for a long time but inactive because they're not connected to Gecko by additional rilproxy/ril-daemons.  This pull request adds those services in `init.goldfish.rc` and overrides Gecko preference __ril.numRadioInterfaces__ to reflect the number of current active modems.

This pull request is for branch [b2g-4.3_r2.1](https://github.com/mozilla-b2g/device_generic_goldfish/tree/b2g-4.3_r2.1), which is forked from AOSP tag [android-4.3_r2.1](https://android.googlesource.com/device/generic/goldfish/+/android-4.3_r2.1).