fix install without static libzmq

[ffontaine]

If libzmq is only available as a shared library and not a static one
then cmake fails with:

-- CMake libzmq package not found, trying again with pkg-config (normal install of zeromq)
-- Found PkgConfig: /home/fabrice/buildroot/output/host/bin/pkg-config (found version "0.28")
CMake Error at CMakeLists.txt:20 (message):
ZeroMQ was not found, neither as a CMake package nor via pkg-config

This is due to the fact that ZeroMQ_FOUND is not set to ON even if
ZEROMQ_LIBRARY is TRUE:

if(ZeroMQ_LIBRARY AND ZeroMQ_STATIC_LIBRARY)
set(ZeroMQ_FOUND ON)
endif()

So change AND by OR as suggested in
#266

Fix #266

Signed-off-by: Fabrice Fontaine fontaine.fabrice@gmail.com

[coveralls]

Pull Request Test Coverage Report for Build 136

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.9%) to 77.226%

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Totals
Change from base Build 135:	0.9%
Covered Lines:	373
Relevant Lines:	483

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