Socktests: Be clearer when plugin cannot be loaded
Socktests: Be clearer when plugin cannot be loaded

Don't fail with a random segfault -- ensure assertion messages are
printed.

Change-Id: I8b7fa91f285d6ab6cf0d33565c17556a234a1ca1
Reviewed-on: http://review.couchbase.org/46744
Tested-by: Mark Nunberg <dab05a0fe859c5cb93882b2a75a0d613501b07be@couchbase.com>
Reviewed-by: Subhashni Balakrishnan <7129c8e37b832c7bd362ff375532d24b98ef5162@gmail.com>

couchbase/libcouchbase,avsej/libcouchbase,maxim-ky/libcouchbase,mody/libcouchbase,signmotion/libcouchbase,couchbase/libcouchbase,avsej/libcouchbase,mody/libcouchbase,avsej/libcouchbase,couchbase/libcouchbase,couchbase/libcouchbase,mody/libcouchbase,PureSwift/libcouchbase,maxim-ky/libcouchbase,avsej/libcouchbase,senthilkumaranb/libcouchbase,couchbase/libcouchbase,kojiromike/libcouchbase,kojiromike/libcouchbase,couchbase/libcouchbase,signmotion/libcouchbase,PureSwift/libcouchbase,PureSwift/libcouchbase,avsej/libcouchbase,kojiromike/libcouchbase,couchbase/libcouchbase,avsej/libcouchbase,maxim-ky/libcouchbase,mody/libcouchbase,signmotion/libcouchbase,kojiromike/libcouchbase,PureSwift/libcouchbase,maxim-ky/libcouchbase,senthilkumaranb/libcouchbase,avsej/libcouchbase,senthilkumaranb/libcouchbase,senthilkumaranb/libcouchbase,signmotion/libcouchbase