tests: rewrite server-test a bit
tests: rewrite server-test a bit

Use setup/teardown functions rather than leaving a single SoupServer
running for the whole test.

jwendell/libsoup,jwendell/libsoup,fanc999/libsoup,jwendell/libsoup,fanc999/libsoup,jwendell/libsoup,fanc999/libsoup,fanc999/libsoup,fanc999/libsoup,jwendell/libsoup