erasure-code: mon, osd etc. depend on the plugins

Since the erasure code plugin version check has been introduced,
whenever a library/binary that can load plugin needs to be recompiled,
the erasure code plugins must also be considered. If the reason for
recompiling the library/binary is a new commit, the plugins will fail to
load.

The dependency is not based on source compilation and a shared library
dependency on liberasure-code.la is added instead. This library is
uniformly used whenever a plugin is to be loaded and therefore covers
all library/binaries that need it.

http://tracker.ceph.com/issues/9413 Fixes: #9413

Signed-off-by: Loic Dachary <loic-201408@dachary.org>