Minimize what we copy to cpiface stage

[krsna1729]

Docker build stage seems to complete once we reduce libraries being copied to cpiface stage

#29 [cpiface 3/5] COPY --from=cpiface-build /opt/grpc/libs/opt /opt/grpc/lib...
#29 ERROR: failed to copy files: userspace copy failed: write /var/lib/docker/overlay2/c6480ij2vovmd28msmoo9b747/merged/opt/grpc/libs/opt/libgrpc_cronet.a: no space left on device
------
 > [cpiface 3/5] COPY --from=cpiface-build /opt/grpc/libs/opt /opt/grpc/libs/opt:
------
failed to solve with frontend dockerfile.v0: failed to build LLB: failed to copy files: userspace copy failed: write /var/lib/docker/overlay2/c6480ij2vovmd28msmoo9b747/merged/opt/grpc/libs/opt/libgrpc_cronet.a: no space left on device
##[error]Process completed with exit code 1.

https://github.com/omec-project/upf-epc/runs/650917611?check_suite_focus=true#step:3:6434
vs

#29 [cpiface-build 8/8] RUN mkdir -p /grpc-libs &&     cp /opt/grpc/libs/opt...
#29 DONE 1.6s

#30 [cpiface 3/5] COPY --from=cpiface-build /grpc-libs /grpc-libs
#30 DONE 1.3s

#31 [cpiface 4/5] RUN echo "/grpc-libs" > /etc/ld.so.conf.d/grpc.conf &&    ...
#31 0.215 /sbin/ldconfig.real: /grpc-libs/libgrpc++.so.1 is not a symbolic link
#31 0.215 
#31 DONE 0.3s

https://github.com/omec-project/upf-epc/runs/651164999?check_suite_focus=true#step:3:6403