Initialization of variable in check_rhev3.pl

Bugfix of Syntaxerror for the attached call.
If only 1 Datacenter exists and the datacenter is not up there is no initialization of the variable 'up'

/githubcheck_rhev3/plugin-dir/check_rhev3.pl -H "MY-IP" -a "MY-LOGIN" -D "MY-DATACENTER" -s status
Use of uninitialized value $comp_state{"up"} in concatenation (.) or string at /github/check_rhev3/plugin-dir/check_rhev3.pl line 1548.
Use of uninitialized value in numeric eq (==) at /github/check_rhev3/plugin-dir/check_rhev3.pl line 1572.
Use of uninitialized value in numeric gt (>) at /github/check_rhev3/plugin-dir/check_rhev3.pl line 1572.
Use of uninitialized value in numeric gt (>) at /github/check_rhev3/plugin-dir/check_rhev3.pl line 1574.
Use of uninitialized value $comp_state{"up"} in concatenation (.) or string at /github/check_rhev3/plugin-dir/check_rhev3.pl line 1577.
RHEV CRITICAL: Datacenters critical - /1 Datacenters with state UP |up=;1;1;0; problematic=1;;;0; uninitialized=0;;;0; not_operational=0;;;0; maintenance=0;;;0; contend=0;;;0; 

Same call after the fix:
RHEV CRITICAL: Datacenters critical - 0/1 Datacenters with state UP |up=0;1;1;0; problematic=1;;;0; uninitialized=0;;;0; not_operational=0;;;0; maintenance=0;;;0; contend=0;;;0;
Merge pull request #22 from Administratoor/patch-1

Initialization of variable in check_rhev3.pl