rebuild creates a broken engine

I'm building QAT engine twice with:

```
RUN cd /QAT_Engine && \
./autogen.sh && \
./configure \
--enable-ipsec_offload \
--enable-multibuff_offload \
--with-multibuff_install_dir=/usr/local \
--with-qat_engine_id=qat-sw && \
make && make install && \
./configure \
--with-qat_dir=/ \
--disable-ipsec_offload \
--disable-multibuff_offload \
--with-qat_install_dir=/usr/lib \
--with-qat_engine_id=qat-hw && \
make && make install
```

This makes `qat-hw` to fail with:
`139655177307456:error:25066067:DSO support routines:dlfcn_load:could not load the shared library:crypto/dso/dso_dlfcn.c:118:filename(/usr/lib64/engines-1.1/qat-hw.so): /usr/lib64/engines-1.1/qat-hw.so: undefined symbol: qat_num_instances`

I could do (i.e., add `make clean`):

```
RUN cd /QAT_Engine && \
./autogen.sh && \
./configure \
--enable-ipsec_offload \
--enable-multibuff_offload \
--with-multibuff_install_dir=/usr/local \
--with-qat_engine_id=qat-sw && \
make clean && \
make && make install && \
./configure \
--with-qat_dir=/ \
--disable-ipsec_offload \
--disable-multibuff_offload \
--with-qat_install_dir=/usr/lib \
--with-qat_engine_id=qat-hw && \
make && make install
```

but that deletes `/usr/lib64/engines-1.1/qat-sw.so` so I loose my first engine.